Welcome to the e30 club. I second the idea of doing some basic maintenance on the car before other things, it will at the very least give you peace of mind and help keep everything in order. A Car will take good care of you if you take good care of it.
After that on an e30 I would really suggest an engine chip and a better suspension because they look so much better lowered. They have great brakes and I wouldn't worry about upgrading the brake package unless you start to reach the limit at the track after upgrading to a good pad and fluid.
Welcome to the site and show us some pictures of your ride!