This build focuses on nuking and CC. The trick is to focus on using Command: Attack and Command: Protectto slow people down with Rylai's Crystal Scepter and use Command: Dissonance to also slow people down.

Greater Mark of Magic Penetration - Need to boost that AP up early on to help with Nukes

Greater Quintessence of Magic Penetration - Even more AP to boost up early on to help with Nukes

Greater Seal of Replenishment - She runs out of mana fast, this will help with early and late game mana issues.

Greater Glyph of Scaling Cooldown Reduction - I used these in combination with the seals to help spam her skills as often as possible.

Teleport - I opted not to use flash or Ghost because she is fast enough when using Command: Dissonance. I use teleport mostly to support my team across the map.

Flash - Since you are a glass cannon you will need all the help you can get to stay alive.

PROS:

Great deny and harrass in early game
Very good damage late game
Buffs Teammates
Debuffs Enemies
extremely nice escape mechanism, coupled with flash (or ghost) it will make you almost
Amazing Support Character
Unique Style of Play

CONS:

Squishy early game
Short range on auto attacks
New playstayle that might be hard to learn quickly

I am going with a 21/0/9 setup for the masteries. Since my goal is to keep her nuke-ability up this seems like the best setup. Again, she ends up being a little less of a support character and more of a nuke/mage.