If you really want the best from your Arcanine in the long run, I would suggest holding off on evolving Growlithe until LV. 48 when it learns Flare Blitz. This will probably be your best physical, stabbing Fire-type move. After you evolve it, then I'd try and get your hands on two Heart Scales and later see the Move Learner where you can then teach Arcanine Extreme Speed (great for finishing off a Pokémon when it's almost fainted) and Thunder Fang (perfect to cover your weakness against Water Types). This will leave your last move for either Crunch which gives you extra coverage or you can keep Flamethower which you can use more often than Flare Blitz; when using Flare Blitz it also inflicts damage on the user which can gradually lead to Arcanine fainting when you calculate the added damage from your opponent.
So, my suggest moveset to use is:Flare Blitz
Extreme Speed
Thunder Fang
Flamethrower
It's pretty much suitable for in-game play and will help you out in a lot of battles. If you do want further suggestions however and have more questions on movesets, then I'd probably use this thread here [link].
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