Hi. This is just a short "guide" I decided to make. It's about my all-time favourite champion, Mundo. Note that this is my first guide, so feedback is greatly appreciated.

Let's jump into it.

You don't really need runes. I've tried this build several times without runes, works perfectly.
However, they will help you in early game. But as I said, runes are OPTIONAL, not necesseary.
Feel free to use your own runes and such, I gathered the ones I prefer to use. BUT, you want to use HP/HP Regen runes. At least some of them...

This is when things are starting to get tricky.

Situational items.

If you're facing a fed Yi, skip the Frozen Mallet and go for a Thornmail instead. See what I mean? Buy items that fits into the situation, like do NOT buy magic resist if you're facing a team full of AD carries.

Harassing

Early game it's all about to harass your enemies with your Q, or slap them with your "axe". Even since your Q deals true damage in percent, nothing will reduce the damage taken. Maxing this early makes the game easier.

Ganking

Ganking before Lv. 6 is useless. Low movement speed, low damage and you probably are a bit squishy. Play defensive until Lv. 6~8. And if you're going in for the kill, use skills in this order:
Burning Agony (W)
Masochism (E)
Infected Cleaver (E)
wait for cooldown
Infected Cleaver (E)
Masochism (E)
Repeat, but without pressing W, and you may wanna use your ult (R)

I am completely new to this, so I don't know what to write here lols. Feedback greatly appreciated, good luck playing!