tribness: I know how Magic Penetration works. Void Staff is typically the last item I build, and only if I see people stacking MR. Usually, though, Haunting Guise+Sorceror's Shoes+Abyssal Scepter actually go very well together in my experience.

Apfeljack: It actually is inspired by Alex Ich. And this build is kind of only something I do if the game is going well, in which case I find Haunting Guise to be a very strong early/mid-game item.

Good content, but too wall-of-textish. Try jhoijhoi's guide on guide building, like the other commenters said. It really is a good guide.

Still, +1 for effort and advice!

Now that looks like a very ALex_Ich inspired build but I like it. It's another way to build Ahri but it seems to work fine.
The only thing I don't really like is the Haunting Guise. I think you can skip that one.
And yes, you need BBCoding.

Haunting Guise + Abyssal Mask + Void Staff dont go well togethet due to the fact how penetrations work.

First you will get the effect from your Abyssal Mask cutting 20 magic resist , then it comes your Sorcerer's Shoes and Haunting Guise meaning a total of 60 magic penetration/reduction and only after you will get the efect from Void Staff cutting 40% of what left. so basically u reduce their magic resist by 60 and then u use the effect of Void Staff wich against most of the targets will be useless. unless u are playing against a full tanky team who is stacking magic resist, this would be a really bad way to use your gold.

Keep in mind that almost all champs will have a value around 40 magic resist, the tanky ones will be higher but the other will be around that. so when your Void Staff comes in to play the effect will be ZERO.

% penetration is good against high magic resist targets. and flat penetration is good against low magic resist targets.

you can find more info here if you are interested
http://www.mobafire.com/league-of-legends/forum/theorycrafting/penetration-y-u-so-misunderstood-15727

Too much text without colours or images. Consider reading this and then if you're still stuck on ideas there's always my guide for inspiration.

+1 for effort.

I prefer DFG over Deathcap for early game when I'm building so aggressively like this. You can disagree, it's just what I like to do. I disagree about Taking just one or the other between Void Staff and Abyssal. Once it gets to late late game, everyone is going to be tanky enough that both will be useful.

I will look up the BBCode stuff. Thanks.

BBCode. You need it. Try jhoijhoi's guide ''How to make a Guide''. Also, You need to rush Rabadon's Deathcap faster. DFG isn't worth it's price till late game where neatly everyone has some tankiness and health. without a deathcap, you have a serious problem in burst and power. Also, take Void Staff or Abyssal Mask, Only in 2% of your games should you need both (a little underestimation but still, rare to get them both as they hinder each other). Take Ryali's or Rod of Ages, Both aren't needed because you get enough health, Other items can give you better AP, and you either want a slow or more mana usually. Just some things to keep in mind, I'm no mid lane expert. ADC and bruiser all the way xD.

Sincerely,

JungleKing