First, ignore anyone telling you it’s a bad idea or not a “proper character”.
Next, don’t put any points into strength but do get athletics and don’t dump str, unless the background is that the tribe put up with him being weaker because of his magic, or that he left the tribe, maybe he hopes to return when he is more powerful and prove himself, etc. or, if you are in a world that treats Goliath differently, maybe that whole “abandon anyone who can’t easily keep up” thing isn’t even there, who knows.
But unless you want to be a gish, there’s no reason to put str above 12 (after racial mod).
Boost int and con, but don’t try to go above 15, and then figure out if he is charismatic, wise, agile, etc.
Then have fun playing a Goliath Wizard.
Reason for a high strength score is green flame blade. You don't have to play it as a typical wizard, its also why I suggested sorcerer as well. If you get into melee you get to use your racial power more.
Dunno. Probably pump intelligence and con, write up a huge background, then dump the whole idea as silly and make a proper character?

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.