This post over on DiscPriest.com is one I found really helpful, even as a babypriest. Disc priest gearing seems very similar to holy paladin gearing, which is good because it won't break my brain.
I love it when they lay out stuff simply, like this stat priority list pulled from that thread:
Caveat: after 1000-1250 int, swapping to the int/spirit gem Seer's Forest Emeralds is more beneficial than the int/mp5 gem.
Some other helpful Disc Priest posts are here and here, on PlusHeal.com's forums.
ETA: Go check out this blog post as well.
Mage Tower Challenges
2 weeks ago