you should wait a couple years for sure (21 is just an arbitrary bare minimum and not a magic age). In those years I would study Anabolic Androgenic Steroids (AAS) (assuming youre well versed in training and nutrition). A list of things IMO you should know in and out:
-anabolic vs androgenic
-Different test. Esters and half lives
-PCT
-HCG
-inject vs oral vs TD
-how to inject (safety, sterile, etc)
-short term side effects and how to treat, long term side effects and how to treat
-gyno (bitch tits)
-steroids and emotional health and stability
now that said, i'll give you an answer (and probably get flamed for doing so) in case you arrogantly decide to ask for our advice and then ignore it completely like a lot of of sub 21 Anabolic Androgenic Steroids (AAS) abusers (IMO anyone under 21 who uses Anabolic Androgenic Steroids (AAS) is abusing steroids). That said...
250mg Test E/ week (in one shot or 2x 125mg) - this is the 'safest' way to go if you decide to risk fucking with your hormones and your natural development.
please be smart, BUT if you chose to be dumb (like i did when i was 20 and did 1-AD) atleast be safe.
P.S. - i highly regret using 1-AD when I was 20 and I'm lucky it didnt fuck me up completely.