Lesser magic essenceFollow

If I remember correctly you've disenchanted armors? Armors mostly give dust and weapons essence. Could be the other way around. But just differ from what you're using now in favor of another to get more essences.

Hope this helps.

This is something I'm starting to use more often before disenchanting an item. thottbot.com search on the item tells you the % chance of getting a particular enchanting item upon disenchant. I have way too much strange dust. So if the item I have has a high % of yielding strange dust then it goes to a vendor or to AH for $$ rather than disenchant. Or you can search thottbot for the enchanting reagent and see the items that yield it, like so Lesser Magic Essence.

Disenchant everything, enchanting regents will usually sell better than the item you disenchanted it from.

and for Mystic essence, I was in stormgarde, arathi highlands. out of everything that dropped i got 14 greater mystic essences