I'm surprised you haven't met a chorus of calls for the 'search' function but this topic comes up nearly every week here haha.
Basic first step: Airbrush - you can easily and safely go cheap - just make sure you get a: Dual-action, gravity fed airbrush.
You'll also need a Compressor, best way to do this is: compressor with separate tank, moisture trap and auto-shutoff.
Then you need accessories like hoses and possibly adapters/fittings and then airbrush mediums and cleaning supplies etc... it's not really a "cheap" sport.