Hey George, welcome to the boards.
It really depends on the kind of compressor you're looking for. If you're looking for a dedicated airbrush compressor (i.e. one of those silent tankless types), I'll let the experts give their advice on those.
I went with a small 3.5 gallon Craftsman compressor. It has a highly adjustable output (I can manipulate it to within half of a PSI) and because of the tank, usually only fills once every other use. Nice thing about it is that it can also power small air tools like nibblers and sanders. It's a bit noisy on fll up, but that only takes about 30 seconds. It cost me about $100 about 2 years ago.
-Fred