i've been playing kog'maw for a long time right now, i notice alot of people build kog'maw with attack speed, i tryed this and didn't like it.i tryed playing him with AP and you'll see it works great.
this is my first guide

i build my runes really AP heavy with magic penetration and ability power

i start the game with boots of speed, because kog'maw doesnt have any escape you need to be mobile at the start. with my boots of speed i buy 2 hp potions and 1 mana potions so that i can stay in lane a bit longer.

when i go back i try to get tear of the goddes for the extra mana so that i can use my living artillary much more, this will come in handy when you are trying to chase someone.
we'll make this in to an archangel staff later

if i need to go back again buy a blasting wand or a needlessly large rod, this depends on how many gold i have. this will give you a nice ap boost and makes you void ooze and living artillery alot more stronger. i try to get my rabadon's deathcap really early cause of the 30 % increase of you AP. this will make all your items alot stronger

when i got enough money i try to get my archangel staff. your tear of the goddes gave you more mana already so the ap of archangel staff is great. especcially with rabadon's deathcap
normally you would have around 350 AP right now. now you can gank alot easier

after my archangel i get my rylai soul scepter this will give you some hp and around 100 ap with rabadon's deathcap. rylai also gives a nice slow so that chasing with your living artillary is super easy.

now i get my lich bane this item is great because it gives you 7% more speed and everytime you use an ability your next regular shot will deal +100% of you AP as dmg. this is great because you have around 600 AP right now so that does alot of extra dmg

finally i get my frozen heart just because of the armor. this will make you very hard to gank

Icathian Surprise - this is you passive, when you die this passive will turn you into a walking bomb. it deals 100dmg plus 25 dmg per lvl. it takes 4 seconds before you'll explode
this is great for killing someone you almost had

Caustic Spittle - this is your Q ability. its passive will give you an attackspeed bonus it start 10% and grows with 5% evrytime you upgrade it.
his active shoots a projectile with 60/110/160/210/260 dmg plus (70%) of your AP. it also reduces the target armor and magic resist.
this ability is great to use when someone is close it will bring is magic resist down so your other skills hit harder.

Bio-Arcane Barrage - this is your W ability. its an ability witch increases your range and deals alot of dmg to tanks. its damage is 2/3/4/5/6% (+0.01)% of the target's maximum Health.
this great when your almost out of mana and you almost got someone.

Void ooze - this is your E ability. this ability launches a path in front of you and evryone you hit with your path is slowed and it does alot of dmg 60/110/160/210/260 + 70% of your AP
i use this after i used Caustic Spittle cause it will slow him and make him easy to hit with
my living artillery

Living Artillery - this is your ulti. this ability shoots an artillery into the air and and comes down again on the place you said it should go. it has a very long range and does alot of dmg against enemy champions. his dmg is 80/120/160 + 30% of your AP, on champions its dmg is increased with 150%.
Each subsequent Living Artillery in the next 6 seconds costs 40/40/40 additional mana (Max 200)
with this ability you have to aim perfectly cause it has a short delay before it lands
when someone runnes away shoot the artillery in front of him

for my summoner spells i use flash and ghost, because kog'maw doesn't have any escape this will give him some more change to get away.

you can also use ignite or exhaust because this makes it easier to gank someone

my first ability i upgrade is void ooze cause of the slow and its nice for farming.
on lvl 2 i get my caustic spittle witch i only use to harras my enemy.
i get void ooze to lvl 5 as fast as i can and put 1 into Bio-Arcane Barrage because of the extra range. so i harras a lot easier after i get my ulti ganking becomes alot easier

when my void ooze is lvl 5 i get my caustic spittle to lvl 5 and after that my bio-arcane barrage

Kog'maw is a great farmer i can destroy a single wave with just one void ooze. but that's after you get you get your rabadons. before that its a little harder but still very easy just shoot your void ooze and then shoot a living artillery on the creeps and you killed them

thanks alot for reading this hoped you liked and learned from it, if you want to say something leave a comment behind

thanks alot

chrisfloor