When Should I Introduce co2 Into my equation?

Im Growing 4 Plants In a non-recirculating DWC system. My Plants Are About 10 in. High And ive just super cropped the main steams for a strong main stalk. Now ive never experimented with co2 and i've been told its the next step along with humidity. I know i can get a co2 system from my local hydro store because ive seen them there, how much would it cost for a system with a "dripper" (timed sprayer idk what they call them but u know what i mean)? And Is It Easy To Use?

btw my grow area is 6x6x8 with 4 plants and im trying 2 scrog a 5x5 canopy. 600w mh/hps but i will b expanding.

no idea how much one costs, but you can introduce co2 right now...promotes faster growth and they will finish sooner if you give the right amounts

you don't need a dripper. for that room get a used 10lb tank. never buy new tanks because when you go to fill it up, most places just do tank swaps. a used 10 lb tank is like 50 or 60. then you can get a regulator on ebay for 60 plus shipping. the grab a co2 ppm controller. get one on ebay for 200. thats all you need.

run a tube from the regulator to the back of a fan.and set the ppm controller on the other side of the room. when the room hits 1500 ppm's the controller will shut it off and when it drops to 1200 ppm's the controller turns it back on. using a controller saves you so much more co2 rather than just using a 15 min timer.