I remember I was playing last night with a couple of my friends in a custom game and doing random 1v1s in a Skype call and goofing around. I figured out that Charm + Fox-Fire make for some decent combos if they're trying to run on me. Spirit Rush was a decent way to close the gap and slam them with Fire or that Orb.
Be careful with spirit rush though, you'll likely want to hang onto it in case you're sure you can get the kill. Because it's pretty useful for escaping.
Which is the case for just about any dash ability.
I used to main Ahri but then I realized that I suck at mid lane. People get smarter and smarter and knows that you can win against ahri if you just avoid her charm. If you waste your charm youre most likely dead if you dont have your ult or flash.