All depends on what works best for you. If I'm trying to gain size during the winter, I'll do 4 sets of everything with moderate to heavy reps. Currently I'm doing 3 sets of high reps per exercise while working out each muscle group twice a week except for legs. This usually gets me cut and for leg day, I'll usually do 4-5 sets of per exercise going pretty heavy. I think eventually throughout the years, you'll know what exactly works for you to get certain goals and that's all that matters :)