If you're going to keep it a while mate I'd consider things in this order, bearing in mind that I didn't and went straight into spending money in the engine on the 996 but if I had my time again I'd do this ...
- Suspension tailored for you
- Riding instruction (to get the most out of it)
- Exhaust (to hear the lovely sounds

)
- Brakes
- Engine
- Engine
- Engine
- Engine
With non-performing bling dispersed equally throughout those options until your wallet bursts!