kennen in my appinion AD kennen if much funner than ap but its personal preferance really.
for my masterys i go 21/9/0 get the magic pen and atk speen masterys and skip leathality because you won't be relighing on crits to much.
i went 9 in defensive becuase kennen is pretty squishy. this build can work just as well if you go with the 9 in the utility tree.
for skills i grab TS above all els and SM when its up.
for runes the only thing i might change is the glyphs to AS but i like the cool down reduction which alows you to harass like no other.
if you notice on the items there all pretty expensive. because there all so expensive i try to get the base items first instead of finishing each item one at a time.
so start out by geting septer then build your boots of swiftness.
next get a bf sword and recurve bow.
next if you need some survivorblilty get giants belt. if not finish your blood thirster then your sword of the devine. next start working on black cleaver. if theres still time in the game left get your phantom dancer and frozen malet
for summoners spells flsh and teleport are good for a mid. if your going side lane i will switch out tele for exahust or ignite.
hope you like the build