Maistre if you can get a regulator for free do it man do it now that will save you at least 140.00 and is the most costly of the setup. Ok now you need a tank here ya go :
http://www.beveragefactory.com/draftbeer/tanks/co2.shtml
Get a 20 pound for 98.00 it cost 18.61 to fill and is good for 2 grows. With shipping you looking at around 135.00 for 20-35 % more bud DO IT MAN!
Above you will see how mine is injected. 3 times per day 12,3,6 let run for 1 minute per cycle depending on the size of the room. My box is small and sealed so you might want to go longer. Good Luck you won't be sorry!
Mr.Wags