Dorans shield: It is fail to buy dorans ring as it gives mana regen... so shield for surivability.(you can also buy amplifying tome and healt potions but you wont be able to play aggresivly.)

Sorcerers shoes: OFC for better dmg with your abilityes.

Hextech revolver/Will of the ancients: Hextech revolver gives you nice ap and spell wamp to help you stay on the lane longer, than you upgrade it to Will of the ancients.

Rylais crystal septer:Gives you nice hp and ap + you can slow enemys with your abilityes so you can stun them easyer.

Rabadons deathcap:This item just increases ap for a huge amounts.

Abyssal scepter and zhonyas hourglass:Great set of AP, magic resist and armor.Plus u can dive with your ulti and activate zhonyas hourglass so u are ivulnerable but ulti is still dmging(great for the teamfights).

So....this is my first guide. I bought kennen 1 week ago and this build is the best of all i tryed... There was a match when i was afk for 7 minutes(blue screen ://) and at the end of the match my score was 11/6/14. So i think this build is nice. If you want to rage or tell that build is good just write me in the comments...