Depending on your size...
I don't have extra money to put into things that only provide a marginal benefit.
Whatever I cannot buy cheaply off ebay or if I cannot make it, I buy it from HTGSupply.
Ebay carbon scrubbers are fine. I bought one hydro bubble unit off ebay to see how it was made and made the rest of mine cheaply. I made my own aeroponic EZ Cloner unit. CO2 isn't worth it in my mind... it's just a hassle with fan timers, etc. Ventilation is very important. Buy your lights from HTGSupply, they come with great warranties and they back up everything and whenever a bulb has gone out on me, I've always gotten another. Buy a grow tent, don't try to skimp there - it's not worth it. I bought a 4.67' x 4.67' one for $200. I believe Technaflora nutes are the best bang for your buck, don't get the super extensive ones and don't try to save the little extra dough by going chemical; you can get their starter kit with everything (including root gel, root solution, bud enhancer) for only $29 and it lasts a long time.
Good luck