Bambi

Hey guys...I am new to the hobby and lucky enough to be given a huge 150 gallon tank. I have some questions and would love some advice/help since I have never set up a reef tank before. My tank is cycling and my main questions and worries keeping me from putting anything in it is all the element control I need. I don't know what to purchase or whos just trying to get my $. I am looking at ATOs and I am stuck at the moment on what's the best one to purchase. I have a Milwaukee Ph MC122 with pump and thinking of returning it to purchase an ATO or monitoring system which include everything and not just the ph. Is there anything out there that controls everything I need automatically during the day? I'm wondering if anyone has used the Kalk King ATO which is for Ph, Alkalinity, calcium and salinity. Which ATOs do you guys use? I'm also confuse on the co2 control...what should I get for co2? Any help is much appreciated. I am taking my time to get it right I would hate to hurt any little buddies I decide to get. Thank you for your help and advice in advance.