Start on his weakest attribute because he's easier to train at 18 years old. Make him a balanced player, dont train anyone else untill he's past 21, single person training every week if possible. You only train free throw and game shape AFTER he's out of his optimum training window around 23-24, before that though, your only goal is to train him.
GEt rid of any competition for his position. Center everything around him. It may be rough in the first year, but near the end of the second year, he will start to show promise.
Ultimately he's your guy, and so ultimately you should decide how you want to use him, just dont train the next 10 weeks in nothing but Jump shot or something like that...he'll be incredibly unbalanced.