Step 1) Make friends with someone who owns or will buy Soraka.
Step 2) Make that friend spec 9/0/21.
Step 3) Make that friend into your personal support b***h.
Step 4) ???
Step 5) Profit
I'm dead serious about this. Anivia uses up mana faster than any other champion. Team up Anivia with a full support Soraka with Clarity and max CDR Infuse, and you will see death and destruction like you never thought possible.
Anivia is probably one of the most destructive champions out there. But she pays a price for this. Most notebly with the mana she consumes and her slow speed. Soraka can greatly help out with the mana issues, and even a bit with the speed, although indirectly. Soraka can't make Anivia faster, but with Soraka's powerful heals, Soraka can help get Anivia to safety in situations where Anivia might otherwise not survive.
When I team up with my friends playing Anivia, I'll go Soraka and we'll annihilate. Even if Anivia goes mid solo to start, I'll try to team up with our tank (hopefully Blitzcrank) and feed our tank mana so they can harass the heck out of the enemy in our lane. Once the laneing phase is over, I stick on Anivia like white on rice. Done properly, you can make the other team think you have two Anivias.