Only use the orb in the beginning if you hit the champ you are against, and the to safe for spell Wamp which is her passive.
Use Fox Fire to hit the champ and herras. In lvl 3 then herras and hit with her Charm so you easly can hit your target champ. be carefull of ganks and use her ulti to chase or escape.

If you are about to lose with this build, then make some simple changes.
Instead of buying a Lich bane, the you should buy a banshee before you buy Rylai's Crystal Scepter.
And dont be the first who goes into the teamfights, be the 4th so you can Charm one and get kill, use ulti for chase in the teamfight IF you are about to win it.
If you are about to lose the teamfight then use ulti to get away, Ahri is not the champ who should sacrifice, because she has a very nice burst and a hurt alot on other champs specially AD carries.

If the champion, you are against in mid lane, herras you, dont use your flash too quickly, deal some damage and if you are about to die, the you need to use flash away, but if you are killing your opponent, then you can flash foward to get a kill. But dont waste it, you can be ganked quickly in mid lane, so remember to ward you lane at the first bush in the water.
use you iginte for champions with life steal/spell wamp, because you iginten reduces their heal with 50%. And if the opponent are walking away alive, then its too bad and you go back to get minion kills and gold.
you have probobly heard it before, but its a good thing to repeat, that there are many who doesnt do this.

Dont use your Orb for lasthitting minions, because it would be waste of mana. Ahri can lasthit minions with autoattack, and she can do it good , but use it once in a while to save up your passive.

In the team battles you need to use you charm on someone who does AOE ulties. because it would interrupt and AOE ulties are dealt by Katarina, Galio, Nunu etc.
Then spam your Fox-Fire to hit 3 targets in the teamfight and orb them all. use Spirit Rush to hunt or kill 2 - 3 oppenents who are low.

2x Doran's Ring are very good to have, becuase of the mana regen in the beginning.
If you buy this, you would be able to herras a lot more.
Buy Sorcerers shoes for som magic penertation, but if you meet a stun team, then buy Mercurys Treads, because that would lower the stuns and cc the enemy could have. Stuns and all kind of cc would eat Ahri alive and she would be dead quick.
Rabaddons Deathcap are very good for the most AP's and this inculdes Ahri, so buy it.
Rylai's are a very good itam because of its slow and you would be able to chase and help your team in the teamfights, so no one gets away from you.
Lich bane would be great, that Ahri have a fine attack speed and you would be able to deal your ammount of AP in that one hit autoattack.