What I actually sounded backwards to me at first, but instead of the big items, Chest, Helms etc I got my Libram, Trinket, and Cloak first. But I am a Pally Tank and not familar with what a mage needs so maybe not helpful to you. However by getting those smaller items I was able to get into some ICC's and was able to gain gear much quicker then.
I am trying to get the 4 pc T10 as fast as possible. I got the pants the other night in VOA. I am just trying to figure out what is the biggest upgrade the head or the chest for me. For mages the 4 pc set bonus is worth getting that before getting the other stuff. Anyone have any idea which piece I should get first?