You're 17. You might not start building good size for another year or so. That doesn't mean it's time for steroids. How long have you really been training for? What's your diet truely like? There are so many other factors to adjust before you start aas. Just because your friends do it and get results doesn't mean anything.
That's exactly what gives this sport a bad name. Kids going around thinking that since others are doing it that it's all good. Research what affects it will have on your very young body. You see the physical results your friends get, it's what you don't see that is the problem.
There's nothing anyone can say that might detour you from starting a cycle, but you're friends doing it and getting results has to be the worst reason to start anything in life IMO