Obvious track prep aside I'd say:

full bushing kit
uprated springs (the choices here are vast)
race seat and steering wheel for control.
car needs a diet
widest, best rubber you can afford


Ok that gets you in the turns with a stock scooby. Get to the turn first and leave it first.

330 brake kit. Stainless hoses all around. New fluid.
Get the motor above 330bhp. Stage I or II sure.

Spend your remaining budget one some driving theory or outright lessons. Make sure the #1 factor (you) is upgraded. Left foot that bugger in to the turns and power out while the scooby runs scared.

I assume the above means a relatively stock WRX since you can't do much to them before you gotta bin that hideous crankshaft.