I'll second what Foxfyre said. The Citadel spraygun is really not worth it, either in build quality or in painting potential,
TBH it's

. Very good quality starter airbrushes can be found for about 60-70$. As for the air supply, you could easily blow through (pun intented) 1 can per session. Not only will the progressive drop in air pressure make it harder to get consistent results, but considering even a quiet starter compressor can be found for as low as 80-90$, you're better off saving your money by not using the air canisters and buying a kit right from the start.
Ebay or Craigslist always have kits for sale in case you are very budget minded.
The key features to look for are a dual-stage, gravity fed airbrush and a quiet non-membrane compressor with built-in water trap.
If you need any help picking out a decent kit, or just have general airbrushing questions, ask away.