Pokemon Black EV Question?

I caught the Volcarona from the Relic Castle, and I want to use it for Battle Subway/Competitive Battling. The thing is, I can't decide how to ev train it. I don't know whether to train it in sp. att/spd, or sp. att/sp. df, or something else. It is a modest nature, so sp. attack up, attack down. Please don't say it is a bad pokemon; it has pretty good stats. I just want suggestions for how to spread the evs, as well as what moves I should have it know.