Fluids are the most important upgrade for the track and the one that should be done *before* your first time out. You can easily boil the OEM DOT3 fluid in both the brakes and the clutch...I've done it and Car & Driver did it 6 years ago when they first reviewed the car.
Motul 600 is good, but Castrol SRF is the best. It's expensive, but you get what you pay for -- I've never boiled SRF and never had to bleed the brakes between events.
After your first day out, you'll likely want pads, tires, and all the other good stuff. But do the fluid first!
