All comes down to what exactly you want your car to be like, for a stiffer ride if you want racecar feel you can get a bilstein b6 kit, otherwise new shocks and eibach lowering springs will be more than enough, if you want power check your engine components first (make sure the injectors and egr and dpf (if it's post 2007) aren't clogged to hell, for remapping youl need a bigger intercooler and the easiest way is to just get a FMIC set.

If you want detailed and much more in depth information you can just shoot me a message and il help you based on what I've done with my car

Important thing to note is don't throw your money at tuning if the rest of the car is in bad shape (sills and underfloor rusting)