Playing Kennen ADC... What? Yup that's what I do. But what's even weirder is that I build him attack speed. The thing is the Hurricane is your baby here. Try to sustain until you get 2500 and buy it right away. This is the bread and butter of the build (along with stattik shiv) the hits from the extra bullets stack your w passive meaning you can use that stacking attack A LOT more. It also stacks your stattik shiv meaning there will be a lot of procs and a ton of aoe from your basic attacks. This also stacks the hextech gunblade, another bonus.
Kennen ADC in general is great. No mana, making him have great sustain. He is insanely mobile with his e and has great poke with w and q and his ult can be game changing. Even if your not building ap, his abilities deal great poke damage and you will be dealing some decent damage throughout the game.