Creatine just puts water in your muscles to make you look bigger. It's a vitamin that helps you retain water, basically. There's more to it, and it does help your muscles, but not much. I know kids who've done it and once they stopped working out they got flabby. Avoid that shit.
Drink a protein shake every morning you plan on working out, which should be three times a week at a legit gym or every night if you're doing it at home with no equipment. More protein, more muscle mass.
Fuck the insanity workout, "muscle confusion" is bullshit and it overworks you. Do what you're comfortable doing and get into your own routine.
This. You have to drink soooooo much water for it to do anything and you can't stop doing it once you've gotten to where you want to be.
My advice to you is to Arnor is to look up some routines and workouts online, to put together a weekly workout plan, and to just do it. Also, weightlifting is great and for our sport and extreme sports it can help make tricks easier and can also help prevent injury whether it's muscular or skeletal injury, but don't forget the tried and true pushups and pullups. Two total body workouts that can get you strong and ripped. So there's some more advice.
Also, you probably don't need to worry so much about the stabalizer muscles thing if you're not going to be trying to do like 800 lbs squats and 400 lbs bench press haha, just standard weight lifting for fitness probably shouldn't mess with you too much, just remember that you need to exercise EVERYTHING.
Have fun!!
Oh and I'm 19, am 5' 10" and weigh ~135-150lbs, it fluctuates because of my jackrabbit metabolism.