Hi my name is pylo, for ppl who play sc2 and watch husky u would get the reference. If not heres a link http://www.youtube.com/watch?v=mXiKttWVgIE. I can't say i am pro or really good at LoL, but I CAN say i rape with rumble in ranked and solo.
Well here is a bunch or reasons y u should play rumble:
1) He is super fun to play
2) He can mid, solo, or duo lane
3) He can zone and harass the **** out of champ who cant heal
4) He is a yordle
5) He has one of the best models in the game
6) Bigfatjiji plays him a lot in toruny or solo

For Summoner Spells, you generally want to get ignite and flash becuase ignite can finish almost dying enemies and reduces heals and flash is just generally a great spell on any chara.
Alternatives: You can also take exhaust, or teleport. For laning and chasing ppl.
You really dont want to take ghost because your shield is like a ghost, so u dont need another one.
And the rest is just not fit for Rumble.

For Masteries I like to go 9/21/0 cuz you can be really tanky and do dmg at the same time. You can also go 9/0/21, but i feel it does not give me enough survivability. I think you can also go 0/21/9 but i do not think it gives enough dmg.

For runes, I usually get magic pen for red, flat armor for yellow, flat mr for blue, and two flat health quints and one magic pen quint. This rune set up gives you a lot of early game advantage, so you can harass and not take much dmg.

You want to max flamethrower first becuase thats your main dmg skill and it combines rly well with ur shield which is y u max shield second. You should get electric harpon on 4 so u can have a slow to catch up to ppl. Always max your ultimate when u can it is really in teamfights or long ranged snipe dying enemies.

For items i generally get boots and 3 health pots to be able to sustain and harass. For first trip back, you usually want to get a hextech rovolver. It is a really good item, it gives decent ap and spell vamp. at a very reasonible cost. Then you would want to get merc. treads to get cc reduction. Your core item is going to be rylais. This item is so good on rumble because it slows, gives u health and decent ap. Deathcap should be your next item because it boost ur dmg output by a lot.

Go play rumble, he is great. Even with the recent nerfs to him, he is still really good and a bit to the OP side. And I know my guide is not that good, it is my first build but I hope you guys can learn something from this.