I have all 7 dragonballs and is on lvl 20 for right now. Is it smart to wish the dragonballs or should I just wait later on when I'm a little stronger.

it depends witch balls you have , if you have the quest balls (tier1) use them now , you can't use those for ssj , if you have the mob ones (tier2) then you could wait if your unique goal in the game is to be blonde and glow a bit , if you actually want to get stronger get a dragonbuff now and gather the balls again while you're still a low level , it will be much harder later on.