Arcane Brilliance: Making your Mage raid-worthy, part 1

A little while after Wrath hit, Arcane Brilliance posted a column on how to gear your Mage up for Naxx. Several things have changed since then:

Pretty much everything I wrote then is now wrong.
You don't really gear for Naxx anymore. Naxx is now a place you go in order to gear up for other places.
Trial of the Champion.
Knowing these things, I thought an updated gearing column might be in order. So if you're raising a fledgling Mage, and level 80 is about to hit you like a truckload of Death Knights, and you're looking for the quickest way to turn green and blue into purple, look no farther. Well maybe a little farther. The column's not over yet.