Ah I see you prefer him solo top.
I usually play him junlge and go for this stuff:

Core:
Merc treads
Frozenheart
Randuins
Wits end/Force of Nature.

I only play him in ranked so I pick what we need. usually if i go jungle/tank it takes up two roles and one of them being jungle is sometimes best left for a carry/assassin. (shaco/twitch/lee sin)

i see we do have a malph discussion here , i also play both jungle and solo top (different builds)

Solo top:

I normally like to go all out tank when i play solo top as malph, mostly because most my mains are tanks,

(Cho Gath, malphite, amumu, Volibear etc.

when i build solo top i normally go

Ninja Tabi/Merc threads (depending on enemy team
Sunfire/Force of nature (depends on what i don't have)
then i build the other item that i didn't get
then i like to go warmogs
into a guardian angel
and to finish it all of i get a randuins omen

which leaves me pretty much unkillable while my e still destroys people

as a jungler i go about it differently

i start out with either regrowth or cloth depending on enemy jungler
work into a philo stone or heart of gold (into a randuins) and sometimes both. then get either of the 2 boots (ninja tabi, merc threads)
then build a force of nature

now it becomes situational
either

guardian angel or Warmogs

after that , if i build guardian angel , i build sunfire and then warmogs
if i build warmogs i go into the guardian angel and finish off with a sunfire

Thing's that are old school aren't necessarily bad.

Shield is the worst dorans by FAR

Not with a solo top Garen IMO, health goes back up to full in a few secs XD. He has no mana either, so I wont even need to recall at all until the jungle is ready to gank and its like you'll seem untouched.

Go bootsx3 health pots on garen if you're solo top so you can actually harass.

if you want standard hp regen go regrowth imo

Wow, you posted without saying fuck for once. Good job.

Doran's is all Kennen needs for early harass. Health regen + armor + extra starting health is better than pots unless you're a really bad kennen.

nocheerios, why you want armor if you go mid on kennen?

makes no sense!

and if you go against ad its better to have boots and exploit your range

doran shield is just a safe way to play kennen because kennen is a safe champion but its not optimum

kennen is pretty easy. you just need to know how to engage/go out. i would advise you to go hextech first . rest is instinct play. also go heal or at least cleanse cause you will get focused for sure in teamfights.