i had an other priority list then the poster before:
Rebounding: i think the most useful skill, but also the most expensiv one
Shot blocking: Guards block more then big guys, or at least on the same level and they don't get paid for this skill - so if i would train blocking then for guards.
Inside defence: Hard to tell how much it brings, most works with OD.
Inside Shot: Nearly makes no difference in scoring output in my team, even with extrem differences.