For a PG, it's best to focus on Outside D and Passing, then the 1 on 1 skills (Jump Shot, Driving, Handling). Shooting Guards need JS, JR, and OD. 
As for SFs, I like to have an all-around guy. Mine has high JS and both defenses, but Passing, Rebounding, and Inside Scoring are right behind.
My PF has high inside skills, but also decent outside outside skills, especially JS. This can create a mismatch, as many PFs don't have great Outside D. 
For a Center, IS, ID, RB, and SB are key. High Passing is also nice, especially if you want to be able to run multiple offenses.