Before you get too carried away on mods, you mentioned this was to be a track car. Is it just for Fun Track Days/Driver Events and such, or do you plan to really compete in SCCA, BMWCCA or other sanctioned racing?
If you are looking to do sanctioned racing, you can't just go willy nilly mod'ing the car, or you will find yourself unclassed, or in an open/misc class. And you WILL NOT be competitive with a mod'ed E30 in an open/misc class, you'll get your ass handed to you.
Other $$$$ assuming you are going track racing (not just AutoX or non-competition track days):
Rollcage - $750 - $1000 (Cutting costs on a cheap rollcage = your life
)
Suspension - $1000 - $2000
Brake upgrade - $800
Tires - $500
Driver's gear (nomex, helmet, 5 pt harness, fire ext, etc.) - $600 - $800