Just keep on trading and like this you can keep doubling yourself which will get more difficult every time cause your capital keeps growing.
it is still possible to double your coins in a gambling game like even in dice games but those games are never recommended becasue they are super risky and you will end up losing a lot more bitcoin if you don't cash out after you have won and that is an important thing to remember in gamblin: to leave after win.
1) Sports : If you think you know about sports then try your luck and win.
2) Dice and alternatives : if you want to try your luck then try these
But all of them are super risky as you said.
"you" only know one way to double your bitcoin and that way is a terrible way too. but that doesn't mean other ways don't exist. you have to look for good investments to make profit on your money not a risky gambling method to lose it all!