What are all Pokémon do you have access to? If you could list some, we could all take it from there.
Arcanine is a pretty good Pokémon on its own, and is able to wreak havoc if used right. If I were you, move-set I would likely be having on it would consist of Solar Beam, Morning Sun, Sunny Day (to lower turns needed to execute Solar Beam, and increase percentage of health gain from Morning Sun), and perhaps Flamethrower (after using Sunny Day, this attack would gain some drastic boost). If you're not much of a huge fan of Flamethrower, you may also try your hands on Flare Blitz; it's equally as good.
As far as EVs are concerned, I'd maximize both its Attack and Speed via raising them by around 252 points or so, and drop remaining 4 to HP. For item, I would recommend either Life Orb or Leftovers. With former, you'd be able to deal more damage with your hits, and with latter, you'll have chance to recover yourself on each and every turn.
Also, this would fit better in In-Game Team Help forum, so if you don't mind, I'll move it there for you!
Moved.