Yeees well, its another AP Kog'maw build.
I have been playing with this build for a while and it seems to work, check out the chapters about laning and such so you understand what you should do with it.
Please rate and all that stuff, remember to try it out.

Pros

Incredible range
Greate damage against squishies
Good at running away (provided that enemies haven't got to you yet)
Greate farmability.

Cons

Can't run away if enemies get to you.
Squishy despite 2,5k health.
Bad against fast champions.
Focused allways.
Requires good aim with skillshots.

You should allways get the middle, you need to get high level fast.

At first levels you should mostly focus on last hits and possibly harassing the enemy with Void Ooze, but take it easy until higher levels, don't rush into enemies.

After you get Living Artrillery it starts being alot easier, just harass enemies with it, but mind the stacks, try not to get over 2 unless necessary.

You should do quite good against many champions in middle, so far mostly just Kassadin and LeBlanc seem hard, as they can silence and move around quite fast. If you harass right you should be able to get a kill by just Flashing a bit forward, shooting void ooze under them and nuking them down with Living Artrillery and Bio-Arcane Barrage

Watch out for ganks, even though you have Flash and Ghost you are very squishy. Yourself you can gank quite well, just open up with Void Ooze and spam them dead with Living Artrillery.

When the game comes to the point where laning stops and people start grouping up, you should stay slightly behind the group, out of the front line. Get manabuff as often as possible and lay Living Artrillery barrage onto them, this makes pushing towers with team easier as you can force them to get away from the turret.

When proper teamfight starts you should stay out of imminite danger and mostly just spam Living Artrillery onto them and shoot Void Ooze. After they (hopefully) start losing the fight you can run after low healthed people and kill them with Living Artrillery, aswell as help to mop up tanks with Bio-Arcane Barrage and Caustic Spittle.

Best-case scenario is that your Living Artrillery gets enemy team low health even before the fight and that helps you win it, and you pick up alot of kills by finishing off fleeing enemies.

If, however, your team loses the team fight and go on the run, you shold throw Void Ooze behind you to slow enemy team and if far enough not to be in too much of a danger, shoot pursuing enemies withLiving Artrillery, if enemies are greedy enough your team and you might even get someone killed by turning around after they have taken enough damage from your Living Artrillery.

For the last item you should get something like Zhonya's Hourglass, Rylai's Crystal Scepter or some defensive item.

There are alot of optional items in the build depending on the match itself.
Usually you don't have to get defensive items because of you are staying away from the most dangerous areas and AoE, but in some cases you justhave to buy some item like Thornmail or Banshee's Veil.

Myes, that's the most of it. Please test out and comment before commenting and leave some "constructive criticism".