It really depends on the offense you want to run and your other trainees.
My opinion, just based on this players skills, is you have time to train two inside skills to a decent level (~13). Because of that, I don't think he will ever become a dominant inside player but has the potential to contribute outside and still defend inside and rebound. I am personally a big believer in rebounding, especially at lower levels where in theory you would have more misses. And he needs a lot of work on rebound which will require a lot of training, i.e. take away from the IS or other inside skills. So if I had to choose two skills to focus on, knowing you might only get 7-8 pops, I would focus on those two skills inside (ID & REB) and then a few pops on the outside.
Here are a few conservative estimates of what you could build:
RNG PF: 12/7/8/9/12/13 - 10/13/13/8
IS Scorer: 12/7/8/9/13/13 - 13/13/9/8
Def SF: 12/7/13/9/12/13 - 11/13/7/8