From my last few days of playing a spiritmaster I have to admit I used wind and water the most. Fire when I don't have wind (or when I'm fighting wind elementals, or things that hit slightly harder and has lower chance to miss). Water is awesome if you're a fan of kiting while you have aggro, it deals the most dps and it sits there to cast, so you can actually play monkey in the middle with the mob. However you don't want to get your pet hit though
water elementals have the least HP from what I've seen.