Ninetales as an attacker

His saving grace is having FS/O and decent bulk. I don't know if I'd use him in a Tier 3 solo unless my other 5 Pokemon could get way ahead of the clock. Arcanine, Typhlosion, Charizard and Blaziken are the unique fire types you want before Ninetales.

I do use Ninetales with Heatwave to attack gyms just because it looks awesome

If you want an off-color Fire Attacker try looking for Torchic, which I've noticed for some reason spawn more during Cloudy Weather (perhaps incorrectly flagged as a Fighting-Type due to its evolution?)

Charizard will also be an incredible Fire attacker if Blast Burn is anything like Frenzy Plant.

If you catch a weather boosted one, why not. However not worth the investment especially when Charmander community day is next.
Might wanna consider Magmar before Ninetales for flavor, iirc it performs better and has an evolution in next generation

I catch and evolve a 2450 Arcanine once a week, maybe it is getting to be hotter where you are and maybe that brings more clear days

I think it's cooler as a defender with Solar Beam countering both rock and water attackers. Buuuuttttt "effective" gym defense is irrelevant to most players...FS/Ov is a great moveset for a Fire attacker, but Ninetales just doesn't have the stats. Vulpix is a fairly common egg I think so it's easy to get a high-IV one that would be okay if you maxed it out. I'd be going for a shiny Blast Burn Charizard on May community day if you want a cool/unusual Fire attacker.

I caught a perfect Volpix once and evolved it and slowly powered it up over a year because it was perfect. It's CP 1988, lvl 34.5 and has FS/OH. According to Pokebattler it often ranks in my top attackers for Tier 3 solo raids and is my 3 best fire type. (I don't have a good Moltres or Flareon so I rely on Entei and Arcainine for fire)

Even with best move Ninetales... Still not worthy to power up...
If you want an additional fire attacker then...
Options:
1. Entie or additional Flareon
2. Ho-Oh, Charizard, Blaziken or Typhlosion...

Good Luck!

At 169 base attack, no, Ninetales isn't even remotely acceptable as an attacker. It's the fire equivalent of slapping the enemy with a wet noodle. And I say this as someone who loves Ninetales's design and has a beautiful maxed Ninetales.