Just getting into airbrushing and need to get everything. Any advice on getting a kit or going piece by piece
Kind of depends on what you want to paint, but as a rule of thumb, buy the best airbrush you can afford, go for a brand name, (cheap ones are generally not well made, and you could get frustrated with your progress not realising the badly made brush is holding you back) and as you are starting out I would suggest one that is that is an all rounder (mentioned before that the iwata hp cs is very versatile, but there are other types and other brands that people like for different reasons.). If you are painting things with a large surface area you might prefer a siphon fed brush as they can hold more paint, (Mitch has a thread at the moment that talks about the merits of a siphon fed brush or a gravity fed brush which you should check out.) I prefer gravity. If you get the chance, try holding some different type of brushes to make sure you are comfortable with them.
Paints...again depends on what you want to do, and whether you want water based or eurothane (I would go for water based to avoid ventilation issues) But I use Wicked paints as again they are versatile and suited to virtually any surface. If you aren't sure just buy black and a reducer to get a feel for it. Then later add white and red, yellow, blue you can mix almost any colour from that. If you aren't sure opaque = a paint that covers things up, and will reach it's colour density and then won't go any darker/deeper. Translucent = a paint that allows the layer beneath to show and will get darker/ more intense the mare layers you apply. Favourite brands are Com art, spectratex, E'tac, Wicked.
Compressor, make sure it has a tank or else it will run constantly, and if you are likely to annoy anyone with noise get a whisper type. If it is second hand make sure it has a working safety cut off valve (or else major kabooms all round), and do an oil check/change and empty out any water. You will need a pressure regulator, water trap, and a connector to join your airbrush to your compressor hose, (will depend on your airbrush choice).
All you need after that (if I haven't forgotten anything) is something to paint on. Print out Mitch's practise sheets, those excercises will drive you mad but ultimately save you months of headaches. Good luck!