Ahri is an amazing champ, packed with great burst damage scaling to AP. And if you're looking for a way to shake up and surprise an enemy team AD Ahri is the way to go.

Now you're probably wondering why on earth you would ever play Ahri as an AD Champion. She has a low costing "stun" (Charm) a nice distance closer (Spirit Rush) and enough damage without AP with her Fox Fire.

Pros
-Extra surprise factor
-Typical mids will be stacking magic res runes instead of armor
-Doesn't use too much mana

Cons
-Slow to start
-If you die once or twice in lane you're basically ****ed
-Hard to catch up when down

We're going for typical AD masteries with a little armor and magic res. Not too complicated.

Armor penetration is a must because as an AP Mage Ahri typically does not have a lot of armor penetration.

Black Cleaver is an alright swap out for an Atmas because you're getting more armor reduction and attack speed.
A second Warmogs if a team begins focusing you it will provide more sustainability.

Leveling up your charm early gives you an early way to harass. IE throwing your charm and getting a couple auto attacks in. Fox Fire is also useful when a champion gets too close or to add more damage when you get closer.

Seriously as Ahri you must, must, must! Play smart. Before and leading up to your Warmogs you will be extremely squishy so please be smart and when in doubt Ignite it out. When engaging an enemy, lead with your charm. And don't forget about your other abilities. Fox Fire is very useful in a close quarters situation and throwing an orb or two never hurts. And please. Don't initiate.

This is my first guide so, hey cut me some lack. But trust me, if you play smart AD Ahri is one hell of a carry.