Sorry if this guide is suckish, it my first. Anyway, I enjoy playing Mundo because A0 he's underplayed, B0 people rarely expect much of him, which comes back to bite them later. Early game, if you're laning, throw cleavers into the bush to make sure no ones hiding, and maybe you can even get a kill. If you're jungleing, start with the red buff, which will help later dealing with the other monsters.

The item purchases (usually)don't matter in their order, but Force of nature is impieritve to survival, esepically against APs.

When Mundo is laneing, your job, as an off-tank/ attack damage champion, is, of course, to take damage! mundo has great regen, so make use of that. Dive in, QWE, back out, cooldown, rinse and reapet. onceSadism comes into play, you can do this almost forever if your cooldowns are low enough and you have the blue buff :)

Warmogs is essential to Mundo's Build, as is Force of nature. Get force of nature first, then Warmogs. Attmas impaler is for later, when you can tank some, deal some.

Order
Red Buff
wolves
Wraiths
Golems
Blue Buff
begin ganking and throwing wards out teh wazzo! you need to keep your jungle route clear to prevent any ganks from happening to your team. Also, if you decide to jungle your enimes forest, use this path
Red Buff
Blue Buff
wolves
Wraiths
Golems
leave one baby lizard in each colored buff zone, so that it doesn't respawn and still shows up on the map.

Mundo has amazing farming. Just Pop W,Burning agony and run around. Your magic penetration should do the trick.