This guide is taken directly from the champion spotlight released by RIOT staff members.
This is my no means my work and I claim no credit for it.

I am posting the guide on here because I find the spotlight build to be rather effective, and until people have had time to experiment with their own custom builds, this could help you too.

Champion Spotlight Play Video

Even amongst yordles, Rumble was always the runt of the litter. As such, he was used to being bullied. In order to survive, he had to be scrappier and more resourceful than his peers. He developed a quick temper and a reputation for getting even, no matter who crossed him. This made him something of a loner, but he didn't mind. He liked to tinker, preferring the company of gadgets, and he could usually be found rummaging through the junkyard. He showed great potential as a mechanic. His teachers recommended him for enrollment at the Yordle Academy of Science and Progress in Piltover, where he may very well have become one of Heimerdinger's esteemed prot�©g�©s, but Rumble refused to go. He believed that Heimerdinger and his associates were ''sellouts,'' trading superior yordle technology to humans for nothing more than a pat on the head while yordles remained the butt of their jokes. When a group of human graduates from the Yordle Academy sailed to Bandle City to visit the place where their mentor was born and raised, Rumble couldn't resist the temptation to see them face-to-face (so to speak). He only intended to get a good look at the humans, but four hours and several choice words later, he returned home bruised and bloodied with an earful about how he was an embarrassment to ''enlightened'' yordles like Heimerdinger. The next morning he left Bandle City without a word, and wasn't seen again for months. When he returned, he was at the helm of a clanking, mechanized monstrosity. He marched it to the center of town amidst dumbfounded onlookers and there announced that he would join the League of Legends to show the world what yordle-tech was really capable of, without hiding behind a foreign banner.

''Ugh, it's gonna take forever to scrape your face off my suit!'' - Rumble

I have changed 1 mastery point in total from the build made on the champion spotlight video.
I removed the single point from "Defense Mastery" and added it to "Harden Skin" for personal preference.

Pro's

• Rather Bulky.
• Can spam skills regularly.
• Great at farming.
• Spamming Scrap Shield speeds you up.
• Nice burst damage.
• Does not rely on mana.
• Forcing an over-heat can help you take down towers.

Con's

• The Equalizer is confusing for the first game or 2.
• When trying to cancel The Equalizer, it can be easy to forget to right click since you are already holding left click.
• Easy to overheat accidentally in team fights

Personally I have played this champion twice so far, and both times very aggressively.
Hitting Flamespitter on cooldown almost all the time and taking short bursts of movement towards your enemy can keep them thinking twice about moving towards the minions. Generally denying last hits rather effectively.

My last game had an enemy Evelynn. Every time she hit stealth I hit Flamespitter and ran towards her, throwing Electro-Harpoon twice in random locations in her general direction. It wasn't until after the laning phase had ended that she actually stunned anybody.

If you know the enemy is coming or if your about to run through a bush, use Scrap Shield and Flamespitter to deter their attack. Each moment of hesitation is a moment to your advantage.

Rumble is a rather unique being, he offtank's pretty well and gets stuck in easily.

When engaged in a teamfight overheating deliberately at the right time can change the tide of battle, but keep an eye on your heat gauge. Overheating accidentally will silence you for around 6 seconds.

Using The Equalizer can finish off fleeing enemies very well, and force enemies giving chase to your team members to take small detours slowing them down, or even turn around. A determined/greedy player will find their health dropping rather quickly if you give chase with [[Flamespitter] active.

If you are running hot and need to cool off, Electro-Harpoon can give your team the vital time needed to achieve what you cannot. Once the enemy is slowed you are free to allow yourself to cool down.

Rumble is the kind of yordle that suits an aggressive playstyle for somebody that wants to help their team. Rumble offers great support as an off tank, with just enough damage so that the enemy cannot afford to ignore him.

You may not be the focused target, but you won't be left till last, make sure you have Scrap Shield for a speedy, safe escape.