Okay everyone, let it be known now that this is my build. Only my opinions are supported here.
Okay, the build above say there are no boots, but the first item you buy is a boot of speed and a health potion, then berserkers greaves. After you have completed the infinity edge simply sell the greaves and swap them out for a void staff.

Thank you for choosing my build.

Pros+ High Damage(for ranged)
High amount of running speed
High attack speed (I was actually hitting faster than Teemo and Master Yi!)
High armor

Cons-
Lower health then most champions
Dangerous to go alone
Prone to ganks

For runes, the one I put are simply the ones I chose. For you, i suggest runes that give you penatration. Such as armor and magic penatration are very important to all ranged. The others above are simply for speed. Movement speed for traveling faster, attack speed for dealing out more damage.

My masteries for Kog'Maw or 21-0-9. This is so I spend les time dead when i do die, and increase the damage I dish out. As for penetration is there in the runes also.

The items i have chosen above are for attack speed, critical chance, attack damage and ability power, along with some mana, and magic penatration. As a bonus, there is also 25 tenacity to reduces stuns, silences, sleeps, fears, slows, blinds and snares.

You start off with a berserkers greaves, onto a cloak and dagger, then a phantom dancer, Madred's BloodRazor, lich bane, infinity edge, then you sell the Berserkers Greaves for a Void Staff.

Skill Sequence does not truly matter, as long as you start off with Bio-Arcane barrage. This way you dish out more damage to those who try to run away from you, also for the hp % it takes out. Along with bloodRazor you can do, 10% magic damage of the enemies hp.

For spells I choose ghost and teleport. You can take any spell that you want for this. But i do not recommend taking anything other than those.

Farming with Kog'Maw is fairly easy. Focus on last hitting minions and try to stick with a teamate while farming. If you need money immediatly, I would try to go out jungling. But remember, have a teamate gaurd you while doing this. If you see multiple minions by each other and have low hp then try void ooze. Please remember this is what I do.

For this chapter to be of any use to you, you must have willing teamates. Try having at least one teamate with you at all times for protection. But if you are feeling safe or gutsy you can go alone and gain more exp. So try to be strong with your teamate and hold together so you can become stronger. If your teamates want to iniate a gank, then be happy to oblige. With Kog'Maw's range and damage you should be okay even in a large team vs team fight.

So overall, this build would be building all of Kog'Maw's stats. Attack damage would be great, attack speed would be amazing. Ability power would be good, penatration would be good also. So this build is perfect for me and it should be good for you to.