advise him that if he doesn't know proper training techniques,and diet that gear isn't going to do shit for him.also tell him that he hasn't reach a very substantial level of muscle maturity,and that he should exhaust all natural means prior to even thinking about trying gear.if he chooses gear at this age it can permanently fuck up his natural testosterone production for life and that he could possibly have to on hormone replacement therapy the rest of his fucking life....all because of not practicing any common sense.
we know that with adults that with proper post cycle therapy natural testosterone production can be kickstarted,with teens however we don't at all.if he doesn't have the patience to earn muscle,put in the time,work and effort he's fucked to begin with....and no amount of gear can ever bail you out of that mindset.