This is just a short and quick guide to playing Kog'Maw in the Proving Grounds.

With this guide you can get a lot of kills regardless of your team composition through destructive magic damage accomplished with mres penetration and reduction and hp shredding.

Just follow the build and kills are ensured. If you have some teammates who can soak up or get the enemy's attention, your work will be easier.

Note that this guide is still under construction but published because it is usable despite the fact.

Pros:
Deal tons of damage
Attack very fast
Capability to snipe enemies
Squishy (Build #1)

Cons:
Low movespeed
Passive harder to aim because of the lack of movespeed

Magic Penetration Reds
Scaling Mana Regen Per 5 Yellows
Scaling AP Blues
Flat AP Quints

You can opt to change:
the Yellows to flat armor
the Blues to scaling magic resist
the Quints to movement speed or flat HP

Don't LEAD.

Remain in the REAR.

Attack when the time is RIPE.

Poke and snipe enemies with

Living Artillery.

Remember to buy health pots. Buy elixirs if you have extra money.

We capitalized on ASPD to take advantage of bloodrazor and kog's bioarcane barrage.
We ramped up our AP to increase bioarcane's max hp threshold damage as well as increase the damage of kog's other active abilities.

In a few seconds any champion will be shredded into bits and pieces. Kog'Maw can make quick work of any champ, tank or carry.

Your role as Kog'Maw is to destroy EVERYTHING. Literally.
Focus on the squishies first and then take out the tanks. However if a lone champion strays into your team, bring him down quickly before enemy reinforcements arrive. 2-5 seconds is enough to bring down that champ, even if you're alone.

Zilean is a very attractive teammate for Kog as he can revive him as well as increase his movespeed to allow for better repositioning in case something goes wrong.

Nidalee for her heals and traps, makes it easier to land Living Artillery

My scores using the build

Stats

End-game

Kog'Maw is a very scary AP Carry that can destroy anyone.

With the removal of Madred's bloodrazor, the closest item to this is Kitae's bloodrazor, which is only available in proving grounds. With massive AP, Kog can deal 10-13% of the enemy's max hp in magic damage per attack, also given his kit, and thus make quick work of any champ, be it tank or squishy.