I used CO2 and Nitrogen before I got my compressor. I picked mine up off eBay for $30 or so. That's exactly what you need. That said, here's what my setup looked like:
Tank and tank regulator were hooked via threaded pipe to secondary regulator. Threaded pipe and T-joint to dueling airbrushes.
Why did he use two regulators, you might ask. I purchased a Paasche regulator which included filter and moisture trap. Plus the regulator was way more precise than the tank regulator. Also, instead of getting threaded pipe, try to get some pipe with a hex head on it. Makes removal 1000x easier!
One other thing: DON'T EVER FORGET TO TURN THE AIR OFF!!!! For some reason I could never get a totally airtight seal on my system. If I left it on too long, when I came down to paint I would be out of gas. Which sucks when the place is only open 9-5 M-F and school and work interfere.
CO2 is super quiet and nice. Just make sure you have enough ventilation (you should anyway!!). Good luck!