Unfortunately, the only Fire-type you may get before the Bug gym is Pansear, who evolves in Simisear with the Fire Stone (which you can obtain in Castelia city, on the first dock, by talking to the first person you see.)
Howeve, having a Fire type (before the third gym in the least) is not really necessary. Against Burgh’s Leavanny, your Tranquill is largely enough to beat him. In White 2, I beat him with a Zubat :)
If you really want a good Fire type, you could choose Pansear, which you can get in the Dreamyard. Litwick is available only after the 5th badge, in the Celestial Tower on Route 7, but Chandelure is among the best Fire types of the game.
Larvesta and Volcarona are available only after the League, and Heatmor is available right on the Victory Road, which is a long way to go.
IMO, I prefer Chandelure. Decent speed, great Special Attack, Defense and Special Defense.
Access to nice moves. Litwick will take some time to evolve when you catch it in Celestial Tower, but I used it several times, and I think he’s totally worth it.