Personally I dont think ur gonna need CO2, atleast not for a couple rounds anyways. This is ur first Hydro grow and believe me u dont want to be thinking about anymore things than u really have to. Hydro is not hard but it does take more of ur time, atleast until u got ur stuff dialed in. Main things in Hydro are 1) PH!!! PH can be a very lil nasty thing to learn to deal with because it will swing allot faster than soil. Good digital meter is a must and always adjust a lil at a time. 2) Aerate your water. no explanation there. 3) Make sure your pump runs. No that is not a joke.
Hydro is simple after u get the hang of it, just pay attention to ur plants and they will tell u what they need.