The best Summoner spells for ahri are :Flash,Ignite and teleport.
With ignite you can get in the early game 2 kills easy.
With Teleport you can gank and help fast of other lanes and you can save towers better.

-Start with a cristalline flask for healing hp and mana. Ahri havent much mana /mana reg in the early time and with the cristalline flask you have everytime 3 heal/mana pots when you come from base.
-Start with a ward. Your Team can need this ward for destroying a invade or save your red buff when your team start with blue

- In the early game buy as first item Seeker´s Armguard. You get Ap and Armor. Armor is very good when the enemy have a ad jungle.
-Chalise of Harmonie : get Magic resi and mana reg. Ahri have in the early game often mana problems and with this item you get more mana reg and magic resi for reduce the dmg from the other midlaner
-Hextech Revolver is a good item for healing and upgrade Ahri´s passiv

-Upgrade your Chalise of Harmonie to Athenes Unholy Grail for More Ap and more Magic resi and more mana reg.
- With the Giants Belt you get more life and you can upgrade this item in the Endgame to Rylais Crystal Scepter. With this item you get many ap and hp becauz ahri die fast when she get the enemy focus.
- Needlessly Large Rod : Upgrade this items in the Endgame to Zonhays

Upgrade your last items when you dont upgrade this in the mid game now to:
- Zohnyas Hourglass
- Rylais Crystal Scepter
- Rabadons Deathcap
- Will of the Ancient

Upgrade first you Q (max Q) for a lot of damage.
Then Upgrade the w for more damage.
And at last the e because you need the e first in time fights and in the teamfights have your other Teammembers a lot of cc too. And Ahri make a lot of damage as APC