The system comes with the regulator, co2 cylinder that you choose, check valve, permaseal and the co2 tubing (10 feet). You will still need a way to diffuse the co2. So either an inline diffuser, in tank diffuser or a reactor.
The other thing to consider is where you will be getting your CO2 refilled. The place where I go uses an exchange program where you give them your empty and they give you a full tank. They don't actually refill your tank for you. It might be best to check someplace close to you to see how they do it. It might not make sense to buy the cylinder if you will be using an exchange program.