Stats!

Intellect, Spirit, Haste, Spell Crit, and Mastery.

Intellect and Mastery are what I think of as direct positive effects, meaning I don't need a bunch of that stat to see a difference, as in 150 Mastery is going to give me around 150 extra absorb potency and 150 Intellect is going to give me 150 more Spell Power + more mana + stronger absorb.

Haste, Crit, and Spirit need a lot of that stat to build up, as in it becomes more useful with the more you have acquired.

My focus as a DISC priest is to give strong absorb effects and heals.

Intellect is 1st priority, it increases your mana pool, heals, bubble's strength, crit chance, and mp5.
Spirit is my 2nd priority, as it regens my mana giving me more longevity as a crucial role in the group.
Haste/Mastery is 3rd, this is a tie for me, because I so badly want to have 1 sec cast time on my Heal, but I also want my Power Word: Shield to absorb 20k damage. I think the best way to sort these stats is to evenly distribute them, even though you need more haste to make a dramatic difference you also need 1k Mastery to increase your Bubble's absorbency by 1k.