Paintball gun question?

I am new to paintballing and would like to buy a gun. I would like to buy a gun in the price range of 250-300 dollars. I want a gun that is good and durable for a beginner, i was looking into a spyder elctra or an smart parts ion, but saw that the ion shouldnt ttake co2 and thats what im primarily going to use because i already have to tanks already filled and wouldnt want to waste them. If i can use a co2 in an ion please tell me and also tell me some other good gun types, Thanks.