if you're planning on producing and selling gold, paypal and sell to bulkers. ask your parents to accompany you to a branch and open an account then tether that to paypal. i don't know who told you you're not old enough for taking ownership of an account, there's no age-limit to access money that belongs to you. you won't have access to a credit line, but at your age, you're better off not spending money you don't have.
if you plan on reselling gold, be doing yourself a favor and leave sythe while you're ahead. profit margins for resellers, not to mention newcomers, are so low right now you're better off finding conventional employment.