What's best for you is to read this
https://forums.steroid.com/anabolic-...-steroids.html
And this
https://forums.steroid.com/anabolic-...es+wrong+young
And ask yourself if you want to spend your 20s having a hard time just getting an erection. Of all times in your life, your 20s.
After having read that and thought about it, spend some years (at least until you're 25) learning how to gain quality weight and how to push yourself hard in the gym. Get yourself to 75kg with abs and even more, and when you can't make any more gains no matter what you try, then consider using AAS.
Check out the diet section and the workout section, there are stickies there that will help you several times more than thinking about dbol or anavar.