My general thought is that for core rating categories (ATH, REB, DEF, BLK, LP for post, SPD, ATH, DEF, BH, P/PER for guards) the goal for a "good" player is 60/70/80 for D3/D2/D1 respectively. That's not to say that a player has to reach that target in all of those core areas. As Trentonjoe mentioned, players tend to fill roles rather than be complete players, especially at D3. So if you need a guy to be a solid post defender it would be good for him to have 60+ in ATH, DEF, and possibly BLK. Guys can certainly be good without hitting 60 in some areas if they make up for it in others, but that's just a general target number I like to shoot for.