Pros

Decent jungle clear
Great for early scuttle fights
Good lane prio
Snowballing champ
High damage abilities
No mana
Versatile build path
Decent scaling

Cons

Heat mechanic
Meele mage
Hard to play if behind

What makes Rumble difficult is his heat mechanic: abilities give heat (Q & W 20 heat, E 10 heat). Reaching 100 heat causes you to become silenced, making you extremely vulnerable. Too many players just spam abilities not considering heat. Having good heat management is key to playing this champ.

Pretty simple: start E lvl 1 & use it to grab cs or to poke your laner. Don't force fights lvl 2-3. Lvl 4 you become stronger. E+Q+E for an electrocute proc, deals a lot damage when put with your abilities. Always rotate to scuttle fights, you should win every time unless you astronomically mess up. You should never be behind during the early game.

Great you have mythic and ult, roam. Just Q the wave and roam. Look to use your ult to force a 3v2 bot or turn a 3v2 bot. This is the part where you strive

You want to group with your team trying to force a 5v5 when you have ult. You melt baron/drag. Can force enemies out of tower with ult. Make picks win game

Start W and begin stacking your heat so you will overheat on your first camp, granting you bonus attack speed. The goal is to overheat with Q on camps to speed up the process. Contest scuttle if you can. Farm till 6 then follow from mid game section

Rumble is a fun champ. Control his heat and control the game

Any feedback is welcome dm on discord (Alchemist Cyanide#5581). Build subject to change as patches and seasons come.