Just going to keep it plain and simple.
Both approaches are very important. Both require consistency, patience and time.
No need for any supplements (legal or illegal)
Bulking = Caloric Surplus
Cutting = Caloric Deficit
Strength/Power = 1-5 reps
Strength Hypertrophy = 6-12 reps
Hypertrophy Endurance = 12-20+ reps
Bottom line To Bulk you have to create a caloric surplus + lifting weights.
To Cut you have to create a caloric deficit either by lowering calories + cardio or one or the other.