When I first bought Kennen I thought "wow what a horrible champion, such a waste of IP." This was also when I was around level 15 on my first account. Later on when I got to level 30 I quickly became tired of the champions I always played and began to give him another try. It was well worth it, what I didn't know is Kennen is based purely on poke and combo. This guide will help you learn both and completely dominate games

I use magic pen marks, health per level seals, ability power per level glyphs and flat ability power quints.
These runes make it so that late game you're not and squishy and do more ability power and early game u have an automatic +15 ability power and magic pen for whatever you might need it for.

I use 0/21/9 for amazing tanky ability throughout the game (not saying u should tank but it's nice for when u get focused) and early exp so you can dominate he lane even more than you will be

I take Flash and Ignite so that you can flash in with your ult after the tank has initiated and ignite so you can kill those annoying kiters

I prefer to start with a dorans shield so that you can poke/harass whatever you want to call it and take a little damage from minions and just heal it back up. after that I get boots of speed and rush a Mejai's. Why a Mejai's you might ask, well i prefer to get it because if you play correctly you will win lane and you will get a few stacks from there but the main reason is because in team fights all you have to do is ult in, practically everyone dies and you can get 1stack-10stacks that and it gives you even more ap when you get your rabadons (if they don't surrender). ;)

Kennen can be aggressive or passive in lane I suggest you don't get aggressive until you reach level 3 so you can combo than lightning rush out. it level 2 you can get your stun out but don't attempt it unless you can get your skill shot out and they're practically begging for it.

What I do when I want to get my combo out is I charge up my W so my next attack adds a mark than I hit w so now they have 2 marks on them. Depending on where the target is I either use my skill shot or rush up with my e and stun them. Kennen is a very dependent on his combo in my opinion. the combo that you use doesn't have to be the one I listed, that one just works best for me. Find what combo works best for you and try to get as many stacks on Mejai's as you can.

All in all Kennen is a very strong champion with a few faults but keep in mind the more you play him the better you will get.