Roadmap

Stage 1: Focus on the Story

Completing the story is the "must do" of the game, as most of the other trophies require a certain portion of this game to be completed first.
Beat all the gelatin dimension levels.
Complete all the balloon dimension levels.
Complete all the old timey dimension levels.
Complete all the gnome dimension levels.
Complete all the robot factory levels.
Beat all the levels in the game.
Collect all the parts and construct your first gadget.

Stage 2: Collect the Tokens and Mod Chips

The tokens and mod chips can be done at the same time, as every token and mod chip required for the platinum can be found in the story mode, although a second playthrough is needed to grab all of them.
Collect all the mod chips in the game.
Collect all of the gold tokens in the gelatin dimension.
Collect all of the gold tokens in the balloon dimension.
Collect all of the gold tokens in the old timey dimension.
Collect all of the gold tokens in the gnome dimension.
Collect all of the gold tokens in the robot factory.
Collect all of the gold tokens assaulting Evil Doof's HQ.
Collect all of the gold tokens across all the dimensions.

Stage 3: Get the Figures

This will be the most annoying trophy in the game, so it's best to get this out of the way as soon as possible, especially after you have unlocked the Free-Play Mode cheat, which makes the arcade games free. This goes along with Stage 4 as some of the figures must be bought with tickets.
Collect every Figure in the game.

Stage 4: Get the Tickets

Tickets are required to unlock several trophies in the list. Try to get as many as possible as early as possible. Tickets are earned by playing the post-level minigames. Like the tokens, tickets act as in-game currency. You use tickets in the post-level store (found on the bottom-left of your TV screen after you beat the level).
Earn 2000 tickets in the course of the game.
Have 500 tickets in your posession at once.

Stage 5: Upgrade Your Gadgets and Weapons

This should come naturally through gameplay. Upgrades are earned by defeating enemies, and mod chips are found in the levels. Aesthetic design chips are earned through playing the minigames.
Install half of the upgrade chips in the game.
Get each and every gadget up to the maximum level.
Collect every upgrade, effect, and mod chip in the game.

Stage 6: Unlock all the Characters and Skins

These two trophies are easily missable. Unlock all the playable characters and all 17 skins by purchasing them in the in-game ticket store.
Unlock every single playable character (Baljeet, Isabella, Pinky, Peter).
Unlock all characters and skins

Stage 7: The Miscellaneous Trophies

Before focusing on the final two trophies, do a clean up run to earn any miscellaneous objective trophies you may have missed.
Get from the treehouse all the way into the sewers as quickly as possible.
Defeat the Gelatin Monster in under 180 seconds.
Climb up the gelatin mountain but never bounce more than once on the same bouncy pad.
Ride the entire balloon barge without falling once.
Run through the bee path in under 38 seconds.
Go across the windy canyon without falling down once.
Stay on the moving platforms for at least 60 seconds. (Don't touch solid ground.)
Defeat 3 enemies with boulders.
Make the Goozim charge into all the gnome village wreckage.
Get through all the crushers without getting hit.
Don't let any cruisers get away. (Shoot them all down.)
Don't miss any button prompts during the giant robot fight.
Don't trip any turret shots by stepping on the laser sensors.
Defeat 3 Dooftron Commanders in the level. (The giant buildings.)

Stage 8: The Boss Fight Trophies

These trophies can only be earned by fighting Doofenshmirtz. They are pretty simple and moderately easy to achieve.
Avoid 4 quad-laser attacks in a row.
Use only the Baseball Launcher to defeat the Doof-Robot.

Tips & Strategies

  • Do not rush, as rushing through the levels can cause you to miss items required for the trophy you are trying to earn.
  • Utilize the co-op feature! While every single trophy can be earned easily enough by yourself, having a partner there to help you will make things even easier and eliminate those pesky A.I. bugs.
  • Revisit the levels to do a cleanup run if you are unsure if you have met all the requirements for a particular trophy. This is especially critical for Figures, Mod Chips and Tokens.
  • Be patient. While this list can be completed in less than 3 days, you may have to do some things over again. No trophy guide is infallible, and no strategy is perfect.
Lifetime Accomplishment Award
Collect every trophy in the game.
9.92%
Very Rare
Platinum
Figure Madman
Collect every Figure in the game.
11.23%
Rare
Gold
This will be one of the most frustrating trophies in the game. In order to earn this trophy, you must find and purchase all 92 Phineas and Ferb action figures in the game. There are 6 that can be found in the story levels, 29 that can be won in the post-level claw game, and 57 that must be purchased in the ticket store. To make it easier earning this trophy, activate the Free-Play cheat (unlocked after earning 36 of the trophies). The cheat allows you to play the minigames without spending your tokens.

Figures found in the levels:
  1. O.W.C.A. PDA. Found in the 5th level of World 1 (To the Gelatin Cork). After killing the gelatin enemies at the beginning of the level, turn to the left and hack a security console. The figure is inside the room.
  2. Perry vs Dessert. Found in the 5th level of World 1 (To the Gelatin Cork). It is located right outside the door that oyu must open by jumping on a gelatin cube.
  3. Jetpack Enemies. Found in the Balloon Dimension, level 3. At the end of the level there are two sets of pink balloon rings. Go through the 5th ring of the second set to find this figure.
  4. Gelatin Monster. Found in the Gnome Dimension, level 2. After talking to Gnome Isabella, defeat the robots and evil gnomes, then take the middle path after the vines disappear. There will be a blue gelatin column that will take you to the second part you need to rebuild the Gem Crusher. Jump in to the column. Underneath some logs and to the right, below a gold token, is the figure.
  5. Sewer Gator. Found in the Robot Factory, level 2. Use the second welding platform (the platforms with the arrows) to nab this figure.
  6. Agent P. found in Doofenshmirtz Evil, Inc., level 3. When using the crane to destroy the Normbots, smash the set of three boxes that are lined up vertically. The capsule is in one of those.
Version 2.0
Install half of the upgrade chips in the game.
34.39%
Uncommon
Silver
This trophy is as simple as it gets. Simply use your gadgets enough that you get enough XP to level them up. Once your gadget has leveled up, access a work bench and apply the upgrade chips. Do this enough times for each gadget and the trophy will unlock.
Modtacular
Collect all the mod chips in the game.
14.21%
Rare
Bronze
Mod chips are the green floating circuit boards in the levels. There are 12 available in the game, two for each gadget. To see how many you have for each gadget, access a work bench, and select the gadget. If there is a "???" on the information box, you are missing a mod.

Use this guide by migueloetb for information on where to find these mods: Mod Chip Text Guide
I'm A-levelin' Mah Gadgets!
Get each and every gadget up to the maximum level.
12.52%
Rare
Bronze
This trophy is very time consuming, but not difficult at all. Simply use your gadgets enough to max out their level (the max level is 4). This is sped up with the Double Gadget XP cheat unlocked.
Chiptastic
Collect every upgrade, effect, and mod chip in the game.
10.72%
Rare
Silver
This is one of the longest trophies in the game. You must fully upgrade every gadget, unlock and buy every SFX chip, and find all 12 mods. As soon as you do that, this trophy will unlock. Take a look at the following trophies for information on how to do each of these things:
Weekend at the Arcade
Earn 2000 tickets in the course of the game.
23.06%
Uncommon
Bronze
Earning 2,000 tickets can easily be done in about 20 minutes, provided you have the tokens to do so. Play the Perry Ball game and try to get as many tickets as possible. Another option (and more frustrating) is to play the prize claw game and try to get some tickets from there. 
Ticket Stockpiler
Have 500 tickets in your posession at once.
32.08%
Uncommon
Silver
This goes along with Bronze Weekend at the Arcade. Simply play the arcade games enough that you earn 500 tickets.
The Full Cast
Unlock every single playable character (Baljeet, Isabella, Pinky, Peter).
20.79%
Uncommon
Silver
This trophy cannot be completed until after you beat the Gnome Dimension (one of the chapters of the story). To unlock this trophy, you must buy Baljeet, Isabella, Agent Pinky, and Peter the Panda from the ticket store. You need about 1,700 tickets to do so.
 
  • Isabella - 100 tickets
  • Baljeet - 350 tickets
  • Agent Pinky - 550 tickets
  • Peter the Panda - 700 tickets

As stated before, tickets can be earned by playing the arcade games in between levels. The quickest way to stockpile on tickets is by playing Perry Ball (the arcade game on the right side of the post-level screen). 
Let's Play Dress-Up
Unlock all characters and skins
13.78%
Rare
Gold
Just as with Gold The Full Cast, these must also be purchased in the ticket store. You will need 2,375 tickets. Skins are costumes that allow players to change how their player character looks. There are 17 additional skins and 4 characters to unlock. 
Gelatin Freedom-Fighter
Beat all the gelatin dimension levels.
59.57%
Common
Bronze
Simply beat all the levels in the gelatin dimension. The levels culminate in a 2 stage boss battle with the gelatin monster.
Up, Up and Away...
Complete all the balloon dimension levels.
50.54%
Common
Bronze
Simply beat all the balloon levels. The levels culminate in an aerial battle across the sky.
That Old Timey Life
Complete all the old timey dimension levels.
46.39%
Uncommon
Bronze
This is a two stage level that starts on a ferry. Simply help Old-Timey Phineas and Old-Timey Isabella fix their tractor and feed the cows to beat the level.
Gnome Toppler
Complete all the gnome dimension levels.
43.80%
Uncommon
Bronze
This one culminates in a boss battle with tthe Goozim, a very large hair beast shaped like a cube. To beat him, enrage him enough that he runs off the side of a cliff. After that, the level will end.
Robot Rioter
Complete all the robot factory levels.
39.87%
Uncommon
Bronze
This level culminates in the destruction of Evil Doof's robot factory and another aerial battle across the skies.
Evil Vanquisher
Beat all the levels in the game.
37.04%
Uncommon
Bronze
This trophy will be earned after defeating the Doof-Robot. 
Gelatin Gold
Collect all of the gold tokens in the gelatin dimension.
15.43%
Rare
Silver
Simply collect all the gold coins in the gelatin dimension. See Gold Dimensional Gold Claim for more information on collecting all gold tokens in the game.
Balloon Gold
Collect all of the gold tokens in the balloon dimension.
18.75%
Rare
Silver
Simply collect all the gold coins in the balloon dimension. See Gold Dimensional Gold Claim for more information on collecting all gold tokens in the game.
There's Gold in Them Thar Hills
Collect all of the gold tokens in the old timey dimension.
17.66%
Rare
Silver
Simply collect all the gold coins in the Old-Timey Dimension. See Gold Dimensional Gold Claim for more information on collecting all gold tokens in the game.
Fantasy Gold
Collect all of the gold tokens in the gnome dimension.
16.22%
Rare
Silver
Simply collect all the gold coins in the gnome dimension. See Gold Dimensional Gold Claim for more information on collecting all gold tokens in the game.
Robotic Gold
Collect all of the gold tokens in the robot factory.
15.82%
Rare
Silver
Simply collect all the gold coins in the robot factory. See Gold Dimensional Gold Claim for more information on collecting all gold tokens in the game.
Evil Doof's Gold
Collect all of the gold tokens assaulting Evil Doof's HQ.
15.43%
Rare
Silver
This trophy is slightly more vague. There are 5 coins scattered around the city. None of them are actually inside Doofenshmirtz Evil, Inc. Aside from one hidden behind the steps of a giant robot, all of them are in plain sight. Take a look at the Gold Dimensional Gold Claim trophy for more information on collecting all gold tokens in the game.
Dimensional Gold Claim
Collect all of the gold tokens across all the dimensions.
13.62%
Rare
Gold
Collecting all gold tokens is an easy, if slightly annoying trophy. This trophy will most likely require two playthroughs. The excellent part of this is that you can revisit any level you want to at any time to find the tokens you've missed. The catch is that you have to replay the level all the way to the end or any tokens you find will be lost. However, you do not have to recollect every token, only the ones you missed. There are 100 tokens across all 5 dimensions, but only certain levels have 5 tokens.

Take a look at the following guide by migueloetb which will help you locate them: Gold Tokens Locations Text Guide.
First Gadget
Collect all the parts and construct your first gadget.
89.32%
Common
Bronze
This will be the first trophy you earn. In the first level of the first dimension, you must find the parts to build a catapult. The parts are stuck in gelatin right in front of the catapult. Simply grab them and build the catapult.
Rush to the Sewers
Get from the treehouse all the way into the sewers as quickly as possible.
34.52%
Uncommon
Bronze
Once you build the radio transmitter in the treehouse in Danville...Almost, slide down the slide and defeat the enemies as fast as possible. Do not collect anything (you can just return later) and enter the manhole. If you get there in under 30 seconds the trophy should unlock.
Gelatin Revolution
Defeat the Gelatin Monster in under 180 seconds.
22.05%
Uncommon
Bronze
This trophy cannot be obtained until you upgrade the Carbonator. Get the Carbonator to level 3 and locate both mods for it to make this trophy easier. Remember to pull the switches as soon as gelatin lands near them and try not to get caught in the gelatin monsters traps. Use your monocoptor to avoid its ground attacks and eat as many of its minions as possible to limit its health regeneration. If you succeed, the trophy will unlock.
Just Bouncy
Climb up the gelatin mountain but never bounce more than once on the same bouncy pad.
19.57%
Rare
Bronze
In the 5th level of the first dimension, there is a stack of green gelatin that you must climb to complete a laser puzzle. Simply bounce your way the gelatin, but do not bounce on the same cube twice. If you mess up, just allow yourself to fall to the floor and try again.
Barging Through
Ride the entire balloon barge without falling once.
17.04%
Rare
Bronze
This trophy is easier than it sounds. In the second level of the balloon dimension you will ride a long row of balloons past some Poke-You-Pines on clouds. They will fire quills at your balloons. Do your best to avoid getting caught and falling. The balloons will reappear after a few seconds. Don't fall, and the trophy is yours.
Agh, Bees!
Run through the bee path in under 38 seconds.
25.47%
Uncommon
Bronze
In the beginning of the fourth level in the balloon dimension you will see a Normbot get destroyed by an angry swarm of bees. They will chase you along a path of balloons. popping them as you go. Simply beat the bees to the exit without falling through the gaps and the trophy will unlock.
Old Timey Winds
Go across the windy canyon without falling down once.
17.29%
Rare
Silver
At the end of the first level of the Old Timey Dimension you will have to cross a windy canyon. Do not fall off of any platforms and the trophy will unlock.
Platform Walker
Stay on the moving platforms for at least 60 seconds. (Don't touch solid ground.)
12.42%
Rare
Bronze
The trophy description is deceitful as you can touch ground, but only on the platform. Do not touch the surrounding area. This can only be done in the Gnome Dimension. At the beginning of the first level there are three rows of moving platforms. Stay on them for 60 seconds. Be sure to hop from one to the other as the platforms fall once they reach a certain point. Do this for 60 seconds and the trophy is yours.
What the Boulder's Cooking
Defeat 3 enemies with boulders.
23.32%
Uncommon
Silver
At the gnome village in the second level of the gnome dimension, take the left-most path up the mountain. There is a rockslide there. Simply lead three Normbots into the slide and the trophy will unlock.
Charging Goozim
Make the Goozim charge into all the gnome village wreckage.
21.03%
Uncommon
Bronze
This trophy is pretty straightforward. The Goozim is the creature Ferb calls a big cube of fur. Make him charge into the wreckage of the village houses before you defeat him and the trophy will unlock.
Cruising through Crushers
Get through all the crushers without getting hit.
13.52%
Rare
Bronze
This is done in the second level of the Robot Factory, Masters of Disguise. Simply avoid being flattened by the crushers on the catwalks.
Cruiser Destroyer
Don't let any cruisers get away. (Shoot them all down.)
33.05%
Uncommon
Bronze
Fourth level of the Robot Factory. The cruisers are the ships with Doofenshmirtz's face on them. Shoot them all down. Use your teamwork skill and rockets to make them blow up faster.
Quick and Timely Champion
Don't miss any button prompts during the giant robot fight.
19.47%
Rare
Bronze
This is the last stage of the Robot Factory. You fight a giant Normbot as Queen Elizabeth. A series of button prompts will appear on-screen. Do not make any mistakes or miss any of them and the trophy will unlock.
Padfoot
Don't trip any turret shots by stepping on the laser sensors.
14.12%
Rare
Bronze
This can only be done during Road to Evil Doof. In this level you will pass through several security paths littered with purple light sensors. Do not step on any of them and the trophy will unlock. I recommend you use Pinky since he is the smallest and there is less chance of tripping the lasers.
Commander Counselor
Defeat 3 Dooftron Commanders in the level. (The giant buildings.)
31.49%
Uncommon
Bronze
In the second level of the final dimension you will battle huge buildings called Dooftrons. There will be three of them. Destroy them all and you will earn the trophy. Use the rockets and teamwork skill to make short work of them.
Laser Tracer
Avoid 4 quad-laser attacks in a row.
10.98%
Rare
Silver
This trophy may cause you the most difficulty. When you battle Doofenshmirtz for the first time, he will use a small sphere that fires several types of bombs, mines, and a penta-laser. The laser starts out as a dual beam and as the battle progresses, shifts into a tri-beam, quad-beam, and finally a penta-beam. You only need to avoid the quad-beam. However, this is harder than it sounds, as Doofenshmirtz has a knack for firing the bombs and mines at the same time he is firing the laser. 

This is also where it gets tricky. Once you get his little sphere to four red dots, do not hit it anymore. Leave it alone, as hitting it again activates the penta-beam, rendering the trophy unobtainable for the duration of the battle. Keep avoiding him until he fires the quad-beam 4 more times. Once he does that, and you avoid the attacks, smash the sphere, and the trophy will unlock.
Grand Slam
Use only the Baseball Launcher to defeat the Doof-Robot.
16.12%
Rare
Silver
The Doof-Robot is the final stage of the game, and the hardest, if going for this trophy, as the Baseball Launcher is useless against the mech's free-floating hands and does no damage to the chassis. You will only have a small window to fire the baseballs into the core of the robot when it exhausts all its energy reserves. After that window is up, it will activate again and trap you in a ray beam. The characters will switch out. Do the same thing two more times and the trophy will unlock.