Build them however you want but these masteries are mainly for high damage especially with the flames.

Alright, here is how the items break down and why

1.Doran's shield: This is so you can stay in the lane longer early game but you will sell it later on if the game gets to about 45 minutes

2.Ninja Tabi: The tabi is mainly so you can have SOME armor for this part of the game plus the dodge chance doesn't hurt.

3.(Optional)Mejais Soulstealer: Now you can start stacking some ability power to make you flames really deadly. Howerver, if your team needs someone to start tanking you should skip this one for now.

(depending on the enemies champs)
4. If they have some deadly Magic users you will wantForce of Nature, otherwise you will wantWarmogs Armor. This is when you start to get really hard to kill.

5. So now that its so hard for them to take down your health, you want a way to bring it up. So build theHextech gunblade. Rumble and this item were meant for each other because of Rumble constantly doing Magic and Physical damage. Start by getting theHextech Revolver first then get theBilgewater Cutlass

6. If there is a pesky mage who keeps taking out chunks of your health, now would be a good time to get the aforementionedForce of nature that is, if you didn't get it already. Otherwise get theWarmogs Armor if you didn't already

7. You may have already sold your shield by now but if you haven't do so and start working forDeathcap

The sequence above is for when you dont plan on ganking first thing. However your team is looking for the lvl 1 team gank just get the harpoon first.

Dont use heal to heal only yourself. Its meant to save your allies who aren't so well endowed as you.