Don't worry about ArPen because until you get higher level's with BiS, etc... gears you won't have enough to make it matter. While lvl'ing I stacked Agi, Ap, and crit. That is just me though the others may have a different opinion. Check a spreadsheet at elitist jerks if you want to be specific, but I think it only has a small amount of gears on the list (all epics I believe, haven't used it in awhile so I could be wrong.)