Clones are better but not a huge amount more. More lumens off lights = more bud. A 1000w light is almost twice as powerful as a 800w light.

Co2 is a real big boost but it's pricey. Appart from that there are only products like pk 13-14 which are used in the final part of flowering to boost the buds using high concentrations of chems which some people say is hard to get the taste of it out. You can use a product like boost accelerator to make sure the plants use up those extra chems more efficiently.