New control arms. (and any worn suspension pieces)
New discs and pads
E30 M3 bushings OEM or urethane. (much better steering feel due to increased caster)
HR sport or race (if your daily driver roads are smooth)
Bilstein Sports or Koni Adjustable.
Bigger rear way bar (S&T bars)
TRACK TIME!!!!!!!!!!
I started doing track days with a 318is. Wonderful car. Had a moderate drop and Bilstein Sports. No sways. Offset front bushings. Car was predictable, safe and fun!
Got hooked and built a 325i spec e30 and went racing. Sway bars made a big difference to turn in and transitions.
Until you can string together a couple dozen laps consistently I wouldn't modify much. Certainly no need for coilovers, heim joints, adjustable rear trailing arms, etc.
Go to
http://www.spece30.com lots of guys there will help you out.