Kog'maw is one of my best champs, so i have decided to post my AD/AP builds for Kog'maw both are woderful builds and i have a great amount of success with both, and i hope you all do as well.

I started only using AD Kog'maw and i love playing him this way bc of the straight dmg that can be dished out in such a short time. AD Kog'maw can dish out 800+ dmg plus 10% of his targets life bar while "W" is active. The first time your opposing team leaves you alone in a lane to push will be their last.

I first played an AP Kog'maw when me and a couple of friends started a 5V5 and i realized that enless i built AP no one on our team could mid properly. AP Kog'maw is the best Mid i have ever played and i have only been beat Mid with this build once by a Malazare.

If i spelled anything wrong pls dont troll just leave a comment about it and ill fix it.

AD- he needs some mag-resist bc he only has 30 at 18 if you don't give him some. the extra atk is just for fun.
AP- i think all Aps need some start off ability power bc you start with 0 if you don't.

Ad- Kog'maw needs boots right off unlike some other champs bc he is very slow without full boots.
Wriggls- is a great item bc even if your not doing so hot it lets you focus on farm to get to the point were you can do some dmg. past that it is rather basic as far as ads go.
Madred's blood razer- this is a great item on Kog'maw bc his Bio-Arcane barrage does 6% of your targets life bar in dmg a shot plus Madred's thats 10% a shot without building Ap.
AP-
Boots of swiftness- so you can run around while droping bombs.
Archangles-staff - So you have lost of mana for spamming.
The Grail- so you can spam your mana away and still get it back rather quickly.
past that its just for ability power.

I do not believe that there is a perfect order for your moves. I think it depends on what you like so the skill sequence is just a subjugation.

Pros- Ad and Ap kog'maw are great at farming, doing alot of dmg, killing tanks fast, and crushing turrets.
Cons- Both Ad and Ap Kog'maw are slow, low HP, Ad- low Mag-resist Ap- low Defence, and both are much better late game then they are early game.

AD- your goals should be to A- get as fed as you can b- burst down turrets C- try not to feed.
Team fight goals A- target the highest dmg out-put champ on the enemy team and watch them vanish B- Do all dmg from a safe distance while behind some one much more brawny than you.
AP- Your goals should be A- clear minions with a click of the mouse so yours are always advancing B- Harass your enemy while he hides behind his turret.
Team fight goals A- focus the enemy's tank with Bio-arcane barrage B- Drop as many Living Artillery s as you can C- pick of runners with Living Artillery.

Your passive is very useful for getting a kill, a double kill or higher after your death, or just making them wast their flash to survive.
When you die you have four seconds to run around and then explode doing high amounts of true dmg.
The most important thing to do when Kog'maw is to realize when you are going to die so you can start to get near your target before you actually die.
This does not mean you should die intentionally.

You are very vulnerable in Jungle bc Kog,maw needs to know who he is targeting he cant just run around and start attacking. I would stay out of jungle except to travel from lane to lane or to run.