Bozo is right, there are many things to get taken care of before Co2...

A few examples of things I would put before Co2 are...

HPS/MH Lighting
Carbon Filter & proper vent/intake
Humidity/ temp gauges (and a way to adjust the humidity)
A grow room you're going to be using for YEARS



A good quote from a very wise person "Keep It Simple, Stoner"

You have no idea how much I overthought things on my first plant... I think I actually killed about 15-20 before I got one to live... Read read and when you can't read, then read some more... I find myself obsessing about growing and end up staring at the screen for hours not gaining one bit of useful info... Don't let it get to you like that, but do read lots.