Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
Hey Everyone, this is my first build so don't be too harsh on me :)
Get dorans and a health pot to start. Many other kennens get an amplifying tome to start but dorans will give you a much better laning phase as the health per 5 is much more than you think. This will also prevent you from having to go back multiple times before level 6 if you are getting harassed too much.
Lane until you really need to go back to heal you have so much gold and can't wait to spend it. Buy the basic boots and whichever part of Rylai's you can afford. Rylai's has a good variety of prices for the snowball items which is why you don't have to go back after you've aquired a certain amount of gold. If you have a little leftover spending gold, buy a few health pots, as they will help significantly to keep you in the lane. Buy the rest of Rylai's and Sorcerer's shoes when you get the gold for them.
Next you are going to want to get abyssal scepter. Buy the Negatron loak first if they have a lot of magic damage but if not just buy the blasting wand. Abyssal Scepter will bring you to about 50 magic pen, which is sometimes more than the magic resist of the other team's carries.
Zhonya's is next. Pretty self explanatory. The game should be ending soon if it hasn't already, so spend excess gold on amplifying tomes for will of the ancients whenever youre at base. The game probably won't last this long, but if it does, finish your will of the ancients and build either a Lich Bane or a Warmogs depending on what you feel would be more beneficial. If your team has good crowd control (lots of stuns, snares, taunts, etc.) then I would recommend Lich Bane because you won't be taking damage at the beginning of teamfights anyways.
How to play as Kennen
You should harass as much as possible with Thundering Shuriken and Electrical Surge. It is useful to save the 5th attack on electrical surge to hit the enemy champions with if they are always surrounded by minions and you can't get them with a Thundering Shuriken. Don't be afraid to use Lightning Rush to get in a good position to Thundering Shuriken them, because energy is awesome. Once you hit level 6, you should be able to go in for a kill, given you are close to full health.
Get your 5th hit from Electrical Surge ready before going in for the kill. You should lightning rush in, and if for some reason you didn't hit them with it, flash onto their character so you aren't energy starved. Usually they will begin to run back towards their tower, allowing you to easily hit them with Thundering Shuriken. Pop Slicing Malestrom, Thundering Shuriken, Electrical Surge, and ignite on them. Usually this ends in a kill, and if it doesn't (because you missed or they are tanks), they certainly have to go back to base and heal.
If you have a laning partner that can hold the lane by themselves or if a tower is down, don't be afraid to try to gank another lane. Use the same technique as you used earlier, as I find it the easiest way to make sure you land all your abilities.
This is the most important part of the game for kennen. You will make or break the game depending on how well you do in the team fights. Kennen's job in team fights is to burst down the enemy carries before they can deal too much damage. Most of the time, this will require you to enter teamfights behind the other team after the fight is initiated. Flash will be your best friend as you instantly get into the team fight with your ulti and begin killing the enemy carries. If you succeed, then all the enemy will have left will be tanks and melee dps. This should be fairly easy to finish off by the rest of your team. If the enemies are expecting you to do this, wait a little bit longer before entering the fight, after they have blown major cooldowns. Rinse and repeat, GG.
Skill Build Explanation:
There are 2 or maybe 3 different ways to build kennen's skill order. The one I use most often is maxing out Thundering Shuriken first. If you are good with this skill shot, leveling it up will have the greatest effect on single targets and easily last hiting minions while laning. The downside is that if you are going for a kill and do not hit the enemy with Thundering Shuriken, you will have very little damage output on that target.
The second way is maxing out Electrical Surge. This will not only increase the on use damage but the passive as well. Maxing this will ensure that you deal a good amount of damage to any given target, since it cannot miss. I would recommend it for beginners while you are still learning the range and width of Thundering Shuriken. Also, maxing out Electrical Surge early will help with farming large groups of minions. At about level 12 or 13 you should be able to kill all the creeps of a wave with Lightning Rush and Electrical Surge. This will substantially increase your exp and gold earned during mid game, allowing you to get abyssal sceptor and zhonya's much quicker.
The third build would be to even out Thundering Shuriken and Electrical Surge. This creates a more constant damage output on enemies rather than a large burst every once in a while. It is pretty much average in the pros and cons of the skill builds above.
Tips and Tricks:
You can use Thundering Shuriken while in Lightning Rush form for a quicker throw to give the enemy less time to react.
Lightning Rush increases your armor and Magic Resist, so during Karthas' or Vlad's ultimate pop it to reduce damage.
If a stealthed unit has at least one mark on them, you can electrical surge to find out their location in order to hit them with another Thundering Shuriken.