#1 environment is the most important, temps, right ph etc
#2 genetics. You won't get fat buds off a strain that doesn't give fat buds.
#3 nutrient quality, get good quality base nutes, additives help but not necessarily needed. Use cal mag and get your ph right first.
#4 lights. You will get just as much from a 400 hps as a 600 if a 600 is making the days too hot. Environment is everything.
Trust me. Environment is everything. The rest can be honed in over time. Avoid autos they are ok but a watered down version of the original strain.
Check out hygrohybrid on you tube. He has a week by week coco grow. Explains all the basics really well.
Again don't underestimate the importance of good environment.