The fact that supplements aren't regulated by the FDA or anyone makes it unsafe. Only after X amount of people die or get permanently f-ed up will the FDA step in.
Supplement does not mean replace. It also doesn't mean magic. Everything you need is in food.
You're 14. You need nothing but food and hard work. This is a good thing. At some point in the next 4 years your body will hit the right stage of puberty and you will see fast and impressive strength and size gains. That only happens if you're working hard. There's no signal or alarm clock that tells you when you hit that phase. Start now and keep going....forever if you want to be big and strong.
That phase during puberty is like being on steroids if you're fueling your body properly and training. Get excited about it and be patient.
Also, watch Bigger, Stronger, Faster on Netflix. There's a segment that shows how ridiculous the supplement industry can be.