Hello! I am OldManBallin26, and this is my first guide so I hope you enjoy it! These next couple of chapters will detail how you should try to play this build and which situations it thrives best in.

I prefer the usual Heal/Flash that most ADCs run, but I have also ran Teleport over Heal when we have a more tanky lineup. Using TP can create quick siege opportunities thanks to his Bio-Arcane Barrage. This could also set up a quick and effective Baron/Dragon take down as well. Be aware that his W gets increased range the more it is upgraded. Having a maxed W plus the Rapid Fire Canon allows Kog to have massive range in any situation.

Most guides you will see for Kog'Maw will tell to build his Q first, but maxing out Kog's w first will maximize his versatility while still being able to carry out plenty of burst damage that most summoners want to see from their adc this season. Maxing Kog's e next provides him enough time to escape from most dangerous situations you might encounter.

So far the best support I've found to go with Kog'Maw is easily Blitzcrank. Blitz's Rocket Grab + Power Fist allows Kog to melt health bars with his R and W. As soon as your support initiates an enemy with their CC skill activate your W and target that champ, and hit your R to get a bit of extra damage. The pair can setup easy first bloods and multiple early game kills that will allow you to snowball to victory. Other Supports such as Alitstar or Bard can also work will with Kog'Maw due to their knock up/stun abilites.

PROS:

Seige potential
Great burst damage
Balanced build allows you to take down almost any champ

Cons:

Not very mobile
can not be very effective if not paired with right Supp

Early game try to last hit as much as possible to save mana for potential kills, but once you complete your Rageblade then you can use W to build stacks and clear waves in mere seconds.
Also late game you should be able to take a baron with just you and a tanky champ (Malphite, Tahm Kench).

Thank you all for your time. This is my first guide so any feedback is appreciated! Have fun and good luck to everybody this season. Ballin out!