If going with an air brush get a decent one and make sure to use a compressor, those cans of air are expensive and last about a minute before freezing up.
Get a dual action top feed (has a cup on top).
Dual action means push down for air and back for paint.
I've has a Iwata HP-C for about 20 years and it still works great.
For a compressor get something with a tank and has a regulator to adjust air flow otherwise you will be replacing your airbrush tip.
Compressors can be found just about anywhere for under $100.
A moisture trap is good to have especially if your in a humid area but not necessary.
Also a decent hose (braided) with quick connect attachments to make removing the brush from the compressor easy.
Coast Airbrush carries all kinds of brushes, there is also
Dickblicks and
Dixie Art.