thats pretty much the basics.
Compressor (or other source of compressed air)
Hose,
Airbrush,(gravity feed just means the way the paint is feed into the brush from a top mounted cup, as oppossed to being sucked up from a glass pot.)
something to mask with if you fancy more than a 1 colour shell,
Paint,
And away you go, but would recommend a face mask (desposable paper ones do the job), stop you getting multi coloured lungs. But thats personal choice not essencial.
And the main ingredients imagination and insparation.....
HTH