AP Miss Fortune

Echo's or you go out of mana after casting 3 times E

Ludens. Her mana costs are insane.

You should play her ap heavy hybrid so you don't have to rely on only e for damage. I go gunblade > cleaver > liandrys > nashors > a bt item, usually GA since she has zero escape. As long as you don't go crazy and use your e to farm, I rarely have Mana issues; just make sure you can hit your q bounces. I top damage charts in almost every game I play that.