Crit = Vers > Mastery = Haste
Crit and Vers are your best stats for a very obvious reason.
Haste and Mastery have no benefit to the direct healing provided by Essence Font, Revival and Refreshing Jade Wind, which are 3 of our biggest healing spells.
Mastery: Gust of Mists can be decent on a fight where you are pumping lots of Vivifys and where raid healing is less important (such as King Rastakhan).
Haste is not useless, but generally does not do as much for us as the other stats.
Blood Elf is arguably the best Horde Race for Mistweaver as it gives us Crit (our best stat) and a small mana gain via Arcane Torrent.
Pandaren is also good for the Food Buff (Epicurean) bonus, and is likely the best Alliance Race.
Weapon: Enchant Weapon - Deadly Navigation
Ring: Enchant Ring - Pact of Critical Strike
Potion: Potion of Replenishment
Food: famine evaluator and snack table
Flask: Greater Flask of the Endless Fathoms
Rune: Battle-Scarred Augment Rune
Also make sure to always use abyssal healing potions for an additional healthstone (they don’t share a cooldown with healthstones).