Many in-game teams suggest Arcanine as a fire type, and it is a pretty good option to say the least. It has great stats, and can hit hard both physically and specially. However, this may not be the fire type for you for the following reasons:
- Arcanine is a stone evolution Pokémon, meaning that in its evolved form, it's not going to learn very many moves. Sure, Growlithe learns Flamethrower at Lv. 34, which isn't that high, however, you'll want more than Flamethrower and Extreme Speed against the Elite Four. If you want a good moveset, you may be stuck with a Growlithe for quite a long time. This is avoidable though, and isn't that big of a deal: just a heads up.
- You mentioned you just received your 3rd gym badge. Growlithe is found at Virbank Complex, so if you want to catch a Growlithe NOW, it will be a pretty low level.
Chandelure is a very powerful fire-type contender, with a special attack stat of 145. However, it is another annoying stone evolution Pokémon. My biggest problem with it however, is that Litwick, its basic form, doesn't evolve into Lampent until Lv. 41, and Litwick is incredibly weak, so training one may be annoying. However, it may be worth it.
Magmortor is also pretty solid. It is decently bulky, and hits pretty hard. It is also backed up by a solid movepool. It evolves by Trading while holding the Magmarizer. This can be a good thing or a bad thing. If you happen to meet these requirements, you can have Magmortor pretty early on. However, if not, well... you won't be able to evolve Magmar.
Darmanitan is another fire-type powerhouse. Of the Pokémon you mentioned, Darmanitan has the least BST, but this is mostly due to a nonexistent special attack stat. Otherwise, you have a hard-hitting physical attacker. Darumaka aslo evolves at Lv. 35, which is pretty low compared to other Gen5 Pokémon. The only problem I see is being relatively frail, but it's fine.
Personally, I prefer Darmanitan, but you may prefer something else. Maybe looking at the advantages and disadvantages of the fire types will help you decide which one is best for you. Hope I helped. :)