Typically I recommend build 1 since it has a great amount of survivability and still does huge damage early and late game. You can fiddle around with build one depending on what the other team has. It also greatly depends what your team has, of course. If you already have 2 off tanks or a tank and another beefy character, you can have fun and do build two and put out some big damage. The doran's ring is just for fun, I have been experimenting with it recently in my build two but even with build two Doran's shield is typically a great item.

It is pretty standard to go for the 9/21/0 build for Rumble. It is obvious that you want the magic penetration with 21 in defense for having survivability and a little increase in your ability power. These are the absolute best runes for Rumble. It gives you a big advantage early game combined with a doran's shield. The Marks and Quint's give your abilities the chance to do some early game damage while the seals give you that dodge chance against melee's that can also proc your mastery to increase your speed. Then the glyphs give you that little bit of early game magic resist.

Ghost and Ignite are the best combination in my opinion. Flash and Exhaust are the only other two that you could consider moving around into that combination. I think that ghost gives you that little bit of speed that sometimes you need to move around the map quickly and be able to help your team out when flash just can't do that. Ignite is very good against certain melee characters who typically can outlast rumble in a 1v1 fight simple because of life steal. It also gives that little bit of extra damage at the end to finish enemies off. Exhuast of course can also be very useful against melee champions but but your E, Ult, and Rylai's you do not need Exhaust as a slow, so it kind of reduces its purposes.

Rumble is amazing early game as well as late game. Rumble at level two is one of the most powerful champions - with the W and Q combo. He is so versatile you can do almost anything with him. If you have a jungle on your team, rumble is good to solo top lane even if against two because if your jungle comes for a gank it is pretty close to impossible to lose that fight. The flamethrower is so great to level with and also harass the other team's melee characters if they come in too close to farm. Rumble should be annoying to lane against. His survivability early game with 21 in defense and magic resist runes as well as the doran's shield should give you a big advantage early game. Always be in the danger zone for the extra damage. With some practice it will get easier to manage that danger zone and not to overheat when you dont need to.

What is there to say about Rumble? With ghost/ignite combo he is best. With the ability to slow with your E, as well as ult, as well as Rylai's no one will escape you. Even if they are fast then you have ghost and they cant go anywhere while you blast out huge damage. I have never really used anything else except ghost/ignite on rumble but you can use ghost if you want to be able to destroy Attack Damage characters easier but with all the slows that come with Rumble, the decrease in damage from exhaust is the only helpful part.