Protein and fat is the key. Muscle needs a base to grow. I never go to the gym, but I made my own home gym lol. All I use is a table saw fence and 6 cinder blocks. I just do hammer curls, awkward bench press, dead lifts, etc. I'm 5'10, 250 and my base has always been built so I'm one of the lucky few who doesn't have to do leg day lol. I just work my upper body and mid body because that's what I mostly use at work.

Protein, Carbs, Fats, Sleep, and make a balanced workout plan or goto bodybuilding.com, I am 15, and a amateur boxer but am also trying to build a great physique, so if you want to chat about it sometime, pm me!

Don't use creatine. It will get you big but once you stop working out, it will turn into water weight.
Eat a lot, 3 meals a day with snacks in between.
Work out a lot, different body parts each day.
After each workout, make sure you eat.
Get plenty of sleep