Ok here we go:
First of all, your spec is good. Your prio to your stats is: 1:Spellpower, 2:Haste, 3:Crit, 4: Spirit.
Rotation: 4 x AB (not 3x) then AM. Then repeat. Only use Arcane Bar when ur walking around and still want to do some dmg. Use ur mana-gem a lot (hit the first one at 80% mana left) and Evocation when needed. I know it takes time to do Evocate, but still you do lots more dmg than "saving ur mana". Try to be "empty" on mana at end of fight, so you do most dmg possible :) (I sometimes (at end of fights) even keep on nuking AB till boss is dead)
Keep in mind that it's like a game how you spend your mana at what time in the fight. If you get the hang of it, you'll looooove Arcane mage :D
Enchant all your gear:
Head: Metagem: +23 crit + 3% more critdamage. And get your headenchant of +30sp and 20 crit. (need to be exalted, check ur guildy's for the wright fraction)
Shoulder: Get your shoulder enchant (24 sp + 15 crit) by reaching exalted by ..? nor sure for Horde, check your guildy's)
Chest: +10 all stats
Bracers: +23 sp
Hands: +28 sp
Pants: Get the +50 sp + 20 spirit one in stead of +50sp + 30 stam.
Feet: Get +12 hit +12 crit
Staff: Get +81 sp in stead of +50
Belt: Get a +23 sp gem in there, not +10 stats.
That will boost ur damage up pretty good.
If you do all that, then all you need is better gear and some nice trinkets. ToC-5 normal drops a Abyss Rune (84 haste + sp-proc) and Talisman of Resurgence (40 Triump-badges) is very nice for Arcane mage (+128 int + use every 2 minutes: 599 sp)
Further, do sjitloads of Dungeons to get Triump-badges. You'll be Tear-9 geared in no time.
Good luck!