The best build to go is AS.i've recently fallen in love with Kog'Maw and since we are discussing about item builds, what is recommended for him? I've seen some hybrid builds mentioned, is that the common one?
Dagger/Doran's Blade
Zerk Greaves
Madred's Bloodrazor
Sword of the Divine
At that point, get Banshee's Veil/Guardian Angel if you need survivability or Infinity Edge/Bloodthirsters/The Black Cleaver if you need more damage.
I'm currently level 27 (almost 28) on the US servers. I play more or less regularly and I have roughly a 1.4 normal game win/loss ratio. I play all types of characters, although I'm strongest at jungling and tanking. I play a mean Amumu, Malphite, and am currently learning Rammus. Add me in-game. Summoner name is the same as my username here.
If anyone is ever looking for builds for LoL, I highly recommend MOBAFire.com. It's a brilliant website with tons of top builds for all champions. LeagueCraft is great too, but MOBAFire has a higher member base.