Well I am kind of in the same boat as you. I am 16, 150lbs., 9% bf, 5'11". So just a little taller and less bf but I am looking to build mass for lax. I am not a pro trainer but I can relay what I have been told by the experts here.
First, yes, focus on a good diet before starting to train. Get a good calorie intake that fits your needs and 175-200g of protein for your weight. I run 200g minimum protein a day and a 4000 calorie intake daily. Your calorie intake will most likely be lower if you are looking to cut, but I think if you eat healthy your metabolism will cut off the fat by itself.
Lean meats. I eat A LOT of chicken and turkey breast because it's very healthy and relatively cheap. Also tuna is a good way to take in protein because it's pretty cheap as well. I would stay away from hamburgers and especially the juicy ones lol. Protein supps are alright to take before/after workout but the great majority of your protein should come in your foods.
Take a multivitamin everyday. This may seem like something that isn't very important but
Multivitamins are very beneficial in many ways you may not think of. Just look at the back of the container, they are loaded with a bunch of goodies. I take magnesium, calcium, and fish oil (omega-3), but that's up to you.
Okaaayyyyy....supps. I have the whole powerchews lineup which is 100% legit. The preworkout gives a great workout, and the BCAAs, glutamine, and creatine chews all taste awesome and are a must have in my routine. Just look around this forum and you'll see all the good reviews they have been given. They're great. I also just ordered some Big Blast which is subbing for Gear until that comes back in stock. When Gear gets back I will probably run Gear, Big Blast, and the powerchews lineup. Big Blast and gear both have blood serum protein. Read all about Gear at: needtobuildmuscle.com. All these products are legit and you will see good results with these, just ask around if your not sure. Hope this helps. I can relate to the spot your in

. You found a great forum and if you want to make progress you should stay on this forum. I've learned so much here. These people know they're sh*t.