Ahri is an amazingly fun champ, and unlike most think she does require skill. Here is a quick guide on how to use ahri and how to PROPERLY build her. there are many average builds, but i currently hav a kda of 10:1 with her and normally dont die more than 3 times. Best game to date with her is 30/3/14! I hope i can help others do as well as i have been doing. Also ps this is my first guide, so it may suck...alot. Enjoy :)

Pros
-Crazy burst
-range taunt ( this is amazing!)
-true damage!
-fun to play
-can 1v1 most champs
-passive spell vamp allows for lain sustain early on

Cons
-squishy till later (unless you follow my build and runes!)
-her escapes are limited to her ult which is also good for damage, causing you to make a decision, survivability or burst?

I run a full 21/0/9. This gets you your burst and allows for you to hang onto your blue!
Some variants go more like 9/0/21, but i like the heavy dmg better. Sorry this chapter is empty :(

So you may wonder why i run Ability power quints, This is simple. Early game. Ahri excels middle to late game, but in early game, without her escape, she can die easily. Early game no one has Magic res, so i take these ability power quints to dish out more damage. Also since Ahri is crazy squishy i take defensive seals and glypsh in order to increase her lane survivability. Because you cant farm, defend, or get kills if you are dead! So survivability in my opinion comes first! Also take 6-9 Mag pen marks for that later game and more ability power 3-0 for early game advantage. These runes are very good for mid, as you will outlast most other mids.

Soul stealer-passive
This passive is good in that it allows for lane survivability. Make sure to hit as many minions as possible with your Q when this is ready!

Orb of Deception-Q
TRUE DAMAGE! this makes Ahri hurt. Mic taunt followed by this allowing for it to hit both ways really hurts. I level this first because 1. works well with passive, and 2. helps farm. This also is good in team fights to throw in a crowded area. Use this ability as much as possible!

Fox-Fire-W
This ability is amazing. Auto locks onto champs so you just press one button and watch their hp drop! Against 1 target this can do more than your Q! It is amazing for late game and helps you get those kills. Its range is surprisingly long and when mixed with your ult, the burst is crazy. Max this second.

Charm-E
The main reason why Ahri is considered OP! Range taunt?! Thank you riot! This move has so many uses! Wanna hit some one with all your abilities? taunt em! Wanna pull some one who is chasing you into your turret? Taunt em! Some one diving you and you need to kite? TAUNT EM! Taunt has saved my butt countless times and has got me countless kills. Taunting some1 is also like casting exhaust in that it shuts them down completly for 2 seconds! Use this ability as defensive and offensive. I always try to open with taunt. BUT if you miss, be careful as you might not hit both times with your Q now.

Spirit Rush-R
Ahri's ult is amazing, but you must be smart with it. It is a good escape and a good way to get a kill. I use it ONLY IF i know i can get the kill, if not save it as you may need to run from a gank! If you have flash up though, you can go more offensive and use it to damage, but if flash is on cd then use this ability wisely. Also if flash and your ult are on CD be SUPER careful. You are a squishy champ with no escape but your R! Taunt can help escape sometimes but not all the time! NEVER use this to initiate unless you are chasing some one who is running from an ally. If you use this ability wisely you will be unstoppable!

I go Flash and Ignite for escape and sure kills. Cant tell you how many people die from ignite. I take that over exhaust any day. Plus if you take summoners wrath you'll gain a nice bonus ap that helps early game. Also flash saves lives! TAKE IT!
Other viable spells besides flash and ignite
Ghost-it ok and has more utility than flash, such as get to places faster
exhaust-you got taunt, take ignite instead
teleport-good for geting back into fight
The rest are eh, dont take.

I always take dorans first then b bak at 750 g for mana crystal and boots, then at 600 go bak for tear. Next save work your way towards rod, Also be sure to upgrade your boots to CDR boots. Nezt get archangels and after that you will want to build a chain vest and then get your hourglass. Get your death cap, and finish off with a lich bane. Now if the match is really long and your pwning face, you can sell your rod of ages and replace it with either Ryjal's crystal scepter for the hp, the ap, and for the slow effect, OR you can build the Void Staff if they are smart and building alot of Magic Res. This build will get you at about 800-900 AP.
Also another option is Mejal's. I build this when i am doing exceptionally well at the start, such as 6/0/6. This item fully staked would replace rod of ages and would offer 20% cd reduction and at full stak greatly increase AP. The only problem is if you keep dying, then this item is not worth it.

So all in all Ahri is a really fun and good champ to use. She does require some skill in that you have to aim with skill shots and that you must know when to attack and when to just hold back. Knowing when to commit for the kill is crucial and after practice you will get it down. So go play some normal games and practice with her. Please leave a comment if you have questions, concerns, or advice on what to do for my next guide. Please do not leave unneeded and harsh comments. Thank you and happy pwning!