It seems as though you copied some of the things said on Ego Ignaxio's guide on solomid. And I mean literally copy pasted. Some parts are original, but.....

I like the guide. I get quints of potency. 15ap is way better than 6% spell vamp. Also lich bane is for 1 on 1 situations. Kennen is a team fighter. You will spam all your abilities and hit zonyas. Lich bane does not help kennen late game. Rylais and WOTA are both way better. You will get 3 autos in a 5v5 teamfight. +1

thanks bro, and here i'll update the items in a second, and for the other stuff thanks for the suggestions i'll look into it. I personally use Ap runes except MPen marks but this is for everyone to help it easier if they dont already know some basics with him. and the replacing is like you said, situational

Not bad...although for some champions you lane vs., like Akali, it's still better to max Q over W. The fact that you can hit her for 200 instead of 150, then follow it for 100 is better than using an auto-attack or weaker Q then chaining it for 150.
Personally, Xerath is really easy to lane against...you move so fast with Lightning Rush, and considering the fact that his Q and R have delays built into them, a well timed Flash and Lightning Rush will easily get rid of his stun.

Runes
I don't feel Greater Quintessence of Spell Vamp is the best for Kennen, 6% spellvamp really sucks, and considering that 3/4 of Kennen's skills are AoE, the spell vamp is reduced to 2%, less than a Doran's Blade. Also, grab AP/lvl blues, they're MUCH more worth Mr/lvl, since you already get Quicksilver Sash. Armor runes or HP/level runes are also better than Ap yellows.

Your Item Order
So I don't understand if you replace all the items, or if the last few are situational. It may be easier to see if you include the core items, then add any situational items into a section dedicated to it. Seems legit though.

That's all! +1,