best advice would be buy some decent protective gear and then mod the bike with whatever money you have left. No point in having a quick as bike and falling off and hurting yourself badly and not being able to ride it.
as far as bike prep goes tho normally stiffen up the suspension a bit (thicker weight oil in front forks and wind up the spring preload in the rear or something along those lines, all depends on how your suspension is already)
As pete has already said gearing is fairly important and cheap, work on your brakes and stuff like IRK will help your engine along nicely.
If its a real tight track play around with things like dropping your front forks say 5mm threw your tripples to make the bike turn in quicker.
If you are actually racing maybe some bark busters incase you decide to bash bars with the other guys racing....
The most important thing (and its normally free) is good maintenance on your bike, adjust the levers to suit your riding position, bar position, tyre pressure to suit the track, ect ect ect