The series has covered the non-blowing cash stuff.

There aren't too many things at 11; options open as you go up. But, since you clearly can make money, I'll mention some of the blowing cash stuff. :) I made a new mage on a new server to play along w/series (and see if my comments were still accurate) and found money no problem (~150g at 10, 550 at 25) so I went gear shopping! Toon is http://www.wowarmory.com/character-sheet.xml?r=Trollbane&n=Foil.

Basically I bought every piece of +spellpower or +fire spell damage (or whatever tree you're in) that was a half-reasonable price. "Of the eagle" is also good, with stam and int. Blues tend to be overpriced.

There are exceptions, mostly crafted ones. At 15 http://www.wowhead.com/?item=43515 is available, often cheap for the power. It can be tough to find a decent one hand to go with it. (I haven't.) JCs make tons of rings leveling, some blue, so it's always worth looking for those. Low level armor patches are almost free so I generally use those over enchants unless it's a really nice piece that will last like the Arugal robes.

There's tons of crafted cloth for mages later. In the 35-45 range there's shadoweave, red mageweave, and dreamweave sets. Can wear that stuff straight to 58 if you want.

Depending on the major glyph you choose it may be as much as 30g, so plan for that expense. Evocation is a strong choice for first major; the added heal is both an
"oh shit" button and time saver. Mount and portal training will also eat some gold. Teleporting = best leveling boost EVER.

Try to get a feel for how much damage your different spells do. Overkill is wasted mana which is wasted time.

Hope that helped. Have fun!