I agree with the other comments, but the only comment I have to include myself is that I dont agree with putting Annies 'E' ability (the shield) points in at level 8. It seems to help me out alot if im being harassed early game by someone with some real range (Kog'Maw). Thats just my opinion.

Long live the magerage.

Good build but shouldnt this be a build for others not a place where you ask questions? :> We have some nice annie builds that look similar, you could ask there, and ask ppl that accualy know what they are doing with the char.

For sure RoA is way better for annie than soulstealer. With your short range spells you will have to be offensive so you are risking alot of stacks while nuking ppl where RoA just skips that part, and gives you realy needed HP.

I would suggest swapping yellow runes for AP/lvl ones. And swapping Ignite for Ghost. She realy needs 2 escape mechanisms. You will not lack the nuke power so ignite is unnessesary.

On the items.
The Guise is useless if you take boots. I would recomend skipping that one. Boots with 20Mpen + 8.55 from runes and 15% from masteries is enaugh if you dont face a MR tank. That is why you should reconsider getting both Void and Scepter. Way better choice would be archangel staff or Rylai, or even lichbane!
Take one of those (void or scepter) when you face tanks with MR ONLY, and check how much Mres they accualy have and decide if 40% will be greater than flat 20Mpen.

On masteries.
The only strange thing is the Utility Mastery. Do you hunt for blue buff often?

Now i have a another build !

It's a nice build but I would buy the rod of ages before you get your mejai's soulstealer.

At best, it's a decent build. I mean, yeah, it gives her a TON of AP, HP, and Mana, but... it's mainly dependent on Mejai's Soulstealer. So it's got a lot of vulnerability to "oh gods my teammates suck and they fed them early game I'm screwed." I'd replace it with a more dependable item, such as Deathfire Grasp; it gives you +60 AP, 15% CD reduction, and has an active that deals 30% of their current health, minimum of 200 damage. With a one-minute cooldown... and it doesn't depend on kills!