Money
Coolers:
Transmission
Oil
Possibly meth not for added power but for insurance
Handling:
Suspension
Tires
Brakes
Performance:
Clutch
Test pipes
Exhaust
Safety:
Gauges
Good tuner
Good installer
That is the starting set, you do not need everything on the list to get going, but having it all would set you up for a good/easy road for awhile.