This is my first guide so don't be afraid to comment.
I have recommended builds for AP, AD, or hybrid, but I myself have only done AP.
I hope that you enjoy the build and that I don't make too many mistakes
Keep in mind this will not show you how to play Kennen but only how to jungle with him

Pros:
can clear jungle camps fast after first buff
has a really nice gank if played right
amazing initiation with Zhonya's Hourglass

Cons:
easily interupted
really strong in lane
squishy

My item choices are pretty straight forward, start with Wriggles and boots and go from there, if you have any suggestions please put them in the comments, if you prefer a different build than the one I give or want to replace any items, I can't stop you.

For my skill sequence on AP kennen, I start with my W to help clear the blue and then E for a quick clear afterword, then I max my Q on AP kennen, my W on AD kennen, and equally on hybrid kennen.

Start at blue and ask for leash, after applying the first mark with your W's passive wait for about 3 basic attacks afterword and use your W with two more basic attacks for the stun-secure with smite.
After blue go to the wolves and basic attack the big wolf until applying a mark, then use E on all three wolves and follow up with W and kill the big wolf before focusing the smaller ones, repeat as necessary on wraithe's and use smite on golems using one pot per camp and one after completing this cycle, you should be lvl 3 ready to gank wherever needed. If no ganks are needed at the time go back and save your final pot.

In ganking, it is necessary to work with your team to cc them long enough to stun them yourself, and pick up an early kill if everything goes right. preferably your ganking for a sion, taric or other champs with auto-stun/snare/suppress so that you can excecute the plan without problem, slow is ok but not preferable unless you're ganking for nasus.