This section is mostly a stub for future work. I intend to have a section discussing pre-MC gear for all of these gear sets.

In general a priest will need 3 sets of gear: 

1. PvE Healing Gear - This gear concentrates on mana, spirit, and healing. Stamina is not as important to the gear set.
2. PvP Healing Gear - This gear differs from the 1st set in that stamina and intelligence is much more important than spirit, mana regen, and healing.
3. Fire Resist Gear - For those priests venturing into Molten Core, this set is essential.  To fight Ragnaros, a priest should have at least 150 fire resist. A side note about FR - green Fire resist gear is a no-no for your set.  This gear typically has no stat benefits other than the priest, and can easily cause you to give up 30 or 40 points of stats.  This is not a good trade off.

Alternatively a priest can also find an additional set of gear useful. A mana regen set of gear is exceptionally useful in situations where a priest is constantly casting, such as fighting Luci in Molten Core.

A final set of gear that a priest will need is a set of Damage.  When questing, or dungeon crawling, never be so shortsighted as to assume that you will remain a non-damage dealer forever.  The transition is much easier if you already have gear in your bank.