Rumble

Top

Scrap and Equalize

Lane bullying and mid-game scaling.

Sorcery

Empowered abilities and resource manipulation

Arcane Comet

Hitting a champion with spells hurls a comet that deals adaptive damage at them. Landing more spells reduces Arcane Comet's cooldown.
Nullifying Orb

Gain a magic damage shield when taken to low health by magic damage.
Transcendence

Gain 10% CDR when you reach level 10. Excess CDR becomes AP or AD, Adaptive.
Scorch

Your first ability hit every 20s burns champions.

Domination

Burst damage and target access

Ghost Poro

When your wards expire they leave behind a Ghost Poro. The ghost poro grants vision until discovered. Gain adaptative force for each ghost poro spawned.
Ravenous Hunter

Heal for a percentage of damage dealt with your abilities. Increases with each unique takedown.

Offense

+5 AD or 9 AP
Flex

+5 AD or 9 AP
Defense

+6 Armor or 8 MR (match-up)

WhyArcane Comet

Proccing Comet on Rumble with either [E] or [R] is likely to result in a hit thanks to the slow. If opting for Rylai's [Q] should become reliable as well. Thanks to Rumble's mana-less, try to abuse Comet by landing as many abilities as possible while it's on cooldown.

WhyNullifying Orb

Nullifying Orb allows you to trade aggressively into AP matchups where you might otherwise risk dying.

WhyTranscendence

Transcendence on Rumble allows you to opt for a heavily Magic Penetration focused build while still being able to keep your teamfight damage up with a little bit of CDR.

WhyScorch

Scorch is rune that is heavily abusable in lane by Rumble with [Q]. The damage scales decently on him as well since he likes to stack Magic Penetration early.

If you think the game is going to get stalled out into 30-40mins+ take Gathering Storm instead.

WhyGhost Poro

Ghost Poro is especially useful on Rumble as the added vision grants you lane safety for when you are pushing. The extra AP when pushed is also great for granting you kill pressure.

WhyRavenous Hunter

Ravenous Hunter allows you to lane aggressively and pseudo frontline with [Q] granting considerable healing.