That depends...how much will you be using them? Can you stand hearing a compressor kick on every couple of minutes? How much do you want to spend?
Ive got one of the larger craftsman compressors(40 gallon or so tank) and it works good. Using an impact you can run it for a while before it kicks on...but for high air consumption tools(grinders, high pressure paint guns, etc) forget it...the noise from it kick on every other minute gets quite annoying to say the least. It will run them no problem, but it does cycle on an off alot. At a minimum look at spending at least 400 bucks to get one that will run air-tools half way decently. I dont really like the oil-less compressors as they are beyond noisy and will rattle your teeth if your anywhere near them. Shop around...hit your local tool stores and do some comparison.