My advice, do your homework, research all kinds of things before you try to reach for pie in the sky goals.

Stay away from cars like nissan 300zx's because they are a pain to work on for a novice.

But the reality of it is, if you don't know what you are doing, then every car is going to be a pain.

Get something popular, that way a lot of people can help you, and parts are more available for it.

I would suggesting starting at like auto trader and seeing what comes up for sale in that price range. Samething on craigslist. Hell, even in the forsale forums on here. That way you have an idea of what you are looking at. Pick a handful of options and start working out a pros and cons list of each one.
Things like, you'll probably be able to pick up a BMW for that price, but what is the insurance going to be like for a teenager with that car?
You could get a early 2000's Tahoe, but are you going to be able to handle the crap for gas mileage?

If your only looking for something cheap, easy to work on, good gas mileage, then find yourself a 5spd honda. Get an older one and save a few stacks of cash. Honda's can be taken apart with a 10mm, 12mm, and a 14mm. I would say they are one of the easiest cars to work on. You ought to be able to find a half way decent 4 door civic. insurance should be decent. and you should get 25+ mpg. With it being 5spd, it will force you to learn how to actually drive, not just push the pedals like most people on the road.
While you are doing all of that, you'll start to find what it is that you like and don't like about your car and other cars on the road, and you can put your money towards that.