Your gun isn't going to shoot itself is it? You're going to need some air. C02 is the cheapest and most readily available source there is, so why not start here? 

• High quality lightweight aluminum Co2 Tanks with industry standard pin valve
• 20 Oz. Tank - Approximately 1100 shots per fill, never have to worry about running out of air mid-game
• 5 Year Hydro Date. We receive fresh tanks monthly. You will not receive out of date tanks
• Safety Burst Disc Pressure Release
• Compatible with all standard co2 paintball guns from the following manufacturers including Tippmann, Spyder, Azodin, JT USA, Valken, Brass Eagle and many other.
• Compatible markers include Cronus, 98, A5, TMC, Alpha Elite, Salvo, Bravo One, Stormer, Kaos, Blitz, Fenix, X7, Sierra One, Victor, Stealth.
• Can be used to run your CO2 Planted Aquarium as well.

All CO2 tanks are shipped empty to comply with Department of Transportation laws. You can fill at your local welding, paintball or sporting goods supply store.