All of the answers you need are here on the forum!
Most power you can get out of your RWD FX35 without major expense - Cold Air Intake, Plenum Spacer, cat-back exhaust & UpRev Osiris TUNE.
For a better feeling ride you can get lowering springs or completely replace the suspension with adjustable coilovers to dial in your ride height and comfort level.
Tons of other things that can be done but these are the biggest and most popular for our platform.
For brands and discussion on this stuff - just use the search bar and the keywords.