Hi everyone, this is my first guide.
I made it because I don't find good guide for Ahri on mobafire.
I play Ahri long time and I hope you enjoy this guide.

CD-cooldown reduction
AP-Ability Power
LB-Lich Bane
RoA-Rod of Ages
CC-Crowd Control
SS-Summoner Spell

Flash-best from escape or gang with ulti CD
Ignite-extra dmg to kill enemy

Others:
Cleanse-good summoner spell as enemy team have a lot of CC
Ghost-insted of flash the better SS you have 3 jumps from ulti ghost don't need
Teleport-good spell for saving your towers from being destroyed and my favourite for solo top
Exhaust-Not my favorite but I've seen people use it on Ahri. Good to prevent people from massacring you, good to escape from, make sure your team can kill a fed carry, but I'd rather leave it to somebody more suited.
Heal-Interesting spell for Ahri, when she's got lifestile from passive and Will of the Ancients and now the heal, you got to fight with 20% heal enemy think then you are free kill, now you hit him with Q and heal and now you got about 60% healthpoint.
Clairvoyance-If your team doesn't have it.

Pros (+)
-massive burst damage
-Good farmer
-good mobility with she's ulti
-ranged charm
-Spirit Rush can go throught from walls
-She's got good ganks
-OP


Cons (-)

-Squishy
-Unusable to lvl 6
-Fox fire attack also minions
-Sometimes banned on Ranked Games

Soul Eater - Ahri gains a charge of Soul Eater whenever one of her spells hits an enemy (max: 3 charges per spell). Upon reaching 9 charges, Ahri's next spell has 35% Spell Vamp. Not really a game breaker. Can be used to exchange harass without taking damage and offers some basic sustain at the game start.

Orb of Deception - Ahri sends out her orb, dealing 40/65/90/115/140 (+0.33) magic damage, and pulls it back dealing 40/65/90/115/140 (+0.33) True damage. Cost 60/65/70/75/80 Mana. Range 880.

Fox-Fire - Ahri releases three fox-fires, which after a short delay lock on and attack nearby enemies. Ahri releases three fox-fires. After a short delay they lock on to nearby enemies (prioritizes champions), dealing 40/70/100/130/160 (+0.38) magic damage. Additional fox-fires that hit the same target deal 50% damage [max damage: 80/140/200/260/320 (+0.75)]. Cost 60 Mana. Range 800.

Charm - Ahri blows a kiss dealing 60/90/120/150/180 (+0.35) magic damage and charming the first enemy it hits, causing them to walk harmlessly towards her for 1/1.25/1.5/1.75/2 second(s).Cost 50/65/80/95/110 Mana. Range 975.

Spirit Rush - Ahri dashes forward and fires essence bolts at 3 nearby enemies (prioritizes champions), dealing 100/140/180 (+0.3) magic damage. Spirit Rush can be cast up to three times within 10 seconds before going on cooldown. Cost 100 Mana. Range 450.

Why not Lich Bane ?

I tried a lot of games for ahri and Lich Bane definitely not.
You must concentrate to Your other spells and no watch for Lich Bane is on cooldown.
And it is very expensive too.You can buy rabadon insted of LB.
More Ap and 30% AP passive.

Why not Rod Of Ages ?

Rod of Ages is not bad item. But it do from Ahri more Ap offtank, you need dmg as Rabadon.
And than you complete build RoA you are level 8-10 and UNIQUE passive: restoring mana and health when you level up is unnecessary now.

Offensive for massive DMG or utillity for CD ?

Definitely offensive (21/0/9) why ?
Because Ahri need Ap dmg from offensive, the CD You can reduct by items (Morelo Of Evil Tome), and Ahri'S spell are automatically short CD.

Total bonus from masteries:
+3 AP
+18 (18.9) AP at level 18
+4% CDR
+10% Mpen
+1.5% damage
+6% damage to targets below 40% health
+increase AP for 5%

Flash CDR -15s
216 Mana at level 18
3 Mana Regen per 5 sec
0,5 Movement speed
+20% buff duriation

The runes I chose is for early game.
I prefer this route for Ahri as it means I can get the most out of Rabadons for one, and

Greater Mark of Insight
The obvious choice for reds. Means spell pen shouldn't be a significant problem until late game. These also means you'll be dealing nearly true damage with your harass early on, which counters for the fact that you have absolutely no AP.

Greater Seal of Replenishment
Honestly not my favorite, but then again there aren't many great yellows. I don't really ever have any mana problems ever. Ahri is limited to her Q in lane and only for harass and farming if things get bad. These runes are essentially for when you're being pushed hard in lane and you need to use your Q to farm.

Greater Glyph of Force
Good for early game, and need AP to massive DMG.

Greater Quintessence of Force
Ap for more DMG, it don't need commentary.

Ahri's role is the AP carry/assassin, therefore you should not be the first into the fight. This means you shouldnt run in first, you because you will probably get killed. If your team is looking for a fight, always wait for the tank/tanky bruiser to initiate before doing anything. Of course, this doesn't mean stand idle, poke at the enemy with when possible but don't rush in. That said, a good Charm onto an enemy squishy is an acceptable initiation and the only type of initiation Ahri is good for. In a teamfight shoot your Orb of Deception into the fray whenever you can. If a target becomes out of place, use your Charm to taunt them into your team for an easy kill. If they escape chase with Fox-Fire. If you are pulled into the enemy team or are caught out of place, use your Spirit Rush to escape. If you cannot return to your team, escape using Spirit Rush through any nearby terrain and retreat or return, which ever is safest.

Summary:
Jump with 1jump from Ulti into fight with second jump sideways a third jump back
meanwhile jumping spam W and Q.

Charm enemy then jump with 1 R into him, then press Q You must hit him because he have still charm!
Then push W and jumping with R.
If target doesn't death, give him Ignite(Summoner Spell).