This topic is a continuously discussed one. Read through the posts and most of your answers will be answered. Use the search feature for more specific questions. The latest issue of FSM has an article that will also help you with many of your questions.
Everyone here will no doubt provide you with their input and preferences, but doing a little reading is what I suggest to you. Asking very general questions could only make the process more confusing. Scan the topics here in the Forum and pick up a copy of the magazine. Also visit the various manufacturers websites, they have very good product information as well.
Once you've gotten to understand the basics, you'll be able to ask specific questions which will lead you to a good decision to which product and accessories best meet your needs and goals.
My arsenal includes airbrushes by Binks, Paasche and Iwata units. I have many in both double and single action. I use'em both. I have a Paasche D3000 compressor. I shoot lacquers, enamels, acrylics and inks.
I'm hoping to get a couple of the new Badgers someday.