Just bought Kennen a few weeks weeks ago and I'm really enjoying him. Just thought I'd reach out to try and improve my gameplay
Thanks all!
is a lot of fun to play. <3
He has at least two different build paths.
You can just build him AP and focus on making teamfight crushing ults.
and 
are your friends here.
You can build him attack speed and use his ult to peel enemies that try to engage on him.
and 
are good choices.
The art of landing a stun without needing to ult is a true test of your skill with Kennen. You can Lightening Rush an opponent to close distance while throwing your Thundering Shuriken (this will make it easier to land the Shuriken) and then activate your Electrical Surge to get the stun down. But normally you should hold your Lightening Rush as an escape tool.
I would say Kennen ADC and Kennen support are still possible, but Kennen mid or top is still your best choice.
If you play Kennen support, then 
is your best start. I know it gives mana, but the gold generation is important and ideally a support Kennen will harass the enemy constantly using Thundering Shuriken. You can upgrade it to 
if you want, but don't complete the item. Playing support Kennen is really difficult because it is so hard to land the stun and this is why Kennen is generally outclassed by supports with more reliable CC tools.
If you play Kennen as an ADC I actually recommend going attack speed APC instead because even if you build AD, Kennen's kit is still essentially AP and magic damage based. Get those 
and use the ult to peel enemies while you AA. Unfortunately, you won't benefit so much from the standard crit builds of ADCs. So you won't do as much damage as an ADC in the late game, but you have a strong mid game and your stun gives you dueling power.
In mid lane or top lane, the standard build is AP and this means you are looking for teamfights with your ultimate. If you kill your opponent in lane, then it often means you had to use your ultimate to do it and when your ultimate is down, you actually do a lot less damage and that often means roaming will be not so effective. I recommend Teleport so that you can always be on the look out for larger fights. You can also use your Lightening Rush to get around the map and be in position for bigger fights. Dragon and Rift Herald are more important to win as of Patch 6.9 and bot lane can become a virtual Clown Fiesta of champions.
Good Luck mastering on the Fields of Justice!
