Each one has it's benefits,

Light is for high damage/blitz, Earth is for tankiness, Fire is for disabling/ignite, Water for healing/durability, Wind is for clones/buffing ninja like Naruto and Gaara, who are common in game.
I would suggest playing Fire until you hit the 80 - 90s, in which then you should try out Water/Lightning depending on the ninjas you have.