Dont get a rotary for your first car. Unless if you want to spent all your time researching how they work and how incredibly different they are from piston'd engines.

If you want reliability, look at an 80s-90s Honda or Toyota. Beat on it all you want, as long as you have bare basic maintenance, it'll NEVER break. If not, look into a diesel...thing. Anything with a diesel will be reliable as well. Also reliable (though slow) would be an N/A rotary.

Fast? DSM. 89-93 turbo..incredibly cheap to make fast. 5.0 fox bodys also, MkIIIs not so much on your budget..most have been abused and need around $1000 in restoration at least. If you can get a nice MkIII for $3500 and spend the other $500 on general maintenance and keep it relatively stock. There's all sorts of info on the forums...anything you can think of has been posted on them before and someone has done it...hell I've seen an MkIII with a Jeep 4x4 swap...put in the 4.0 I6 and the 4WD off of it as well.

Cheap? Any generic car made before 95. Most domestics (generic ones, not like the fox or f bodies) wont be very reliable at all, and all the reliable cars are slow.

The two things to remember most about cars :cheap, fast, reliable. Pick two. Also, learn how cars work and all the little things about them, and learn how truely little about them you know. The more you find out, the less you know.