E36 M3 hands down and this is coming from someone with over 15 weekends just at Road Atlanta in various cars and atleast another 6-10 at other tracks.. One of the best chassis on any car of all time. Ranked best handling car for any price in America when it was out and still nationally competitive in SCCA autocross against the most built Evo's. Also, the only car club raced more seems to be Miata's but Miata's have no balls. Predictable and easy to drive fast as well. With modest upgrades you will have no trouble running down just about anything from Vette's to Elise's.. Mine is doing 1:43's with shocks/springs/R comps only! and some power upgrades. You'd have to be very on top of things to match a 1:43 in a C5 Z06 on R comps. I only get passed by instructors and club racers in Vette's...never students..
I would suggest an E30 to learn on (incredibly predicatble and what I learned on) but in terms of handling their rear supsension design/geometry is really inferior compared to an E36 and they just don't handle nearly as well. Put it this way Mike McCoy's gutted and nearly stock E36 325is (shocks, springs, software, 2600lbs) runs better times on street tires then your average spec E30 race car (we run down Robert Patton every event and he "had" or still "has" the spec E30 record on Road Atlanta).
Also E36 M50 based motors are bullet proof. I'm at around 140,000 miles and so many of those are hard hard track miles and I've done nothing but a clutch and oil changes. More solid than any track car in my own personal opinions.
I'd also suggest (if you really like Corvette's an older 98-99 C5 vette). They are cheap to run and with skill can be very fast but they are NOT the best tool for learning at all.
I can't really suggest anything else because the E36 chassis is so good for so cheap and SO much fun to drive. My family friends all had CRX's back in the day and I loved driving those (incredibly fun and easy to learn from and maintain) but I just can't deal with FF.
I would NOT by any means every suggest an S2k. Incredibly switchy at the limit and are really driven best by those with LOTS of experience and talent. You have to be on your feet with ALL your skill in tact to drive one at the limit lap after lap, otherwise you just have to back off if you don't have the skill. If you start going to track days I gaurentee you'll see beginners spinning left and right and going off in S2k's.