Campaign is relatively easy, I focussed on getting achievements as they will be needed for challenges.
I recommend doing the 23 challenges I completed as they are the easiest in my opinion.
For greater than 90% damage at garage and don’t take any damage I recommend starting a new game and doing it on first level.
For collect all soulons I recommend doing it on second level, when they are unlocked.
The rest can be done by repeating the last level until you have them
The Richest Man – 27:16
Hot Pursuit – 28:21
Crazy Jumper – 30:00
Driver’s Licence – 32:26
Chopper’s Mania – 33:46
I Will Survive – 35:23