You will need to check what gun you want, and match a compressor to the scfm the gun needs to operate. Larger capacity tank will help, and you will need a good line filter as well. If you can afford an air dryer I would highly recommend at refrigerated system over desiccant.
You will also need to match the gun to the supplies you are painting. Each material will suggest a different fluid tip. I prefer Iwata guns as you can interchange fluid tips without change needles like a Sata.