Elemental exploits do help a bit. There are three different elements in this game: earth, fire, and shadow. Earth beats fire, fire beats shadow, and shadow beats earth.
During fights elemental weakness adds around 10-15 power to your overall attack power.
The outcome of a match is determined solely through three factors:
Your champ's base power - affected by how high your champ's level is and whatever equipment they have on.
The training results - rain regularly to keep your character ahead of the competition. At least once between each fight.
Hitting an elemental weakness.
Straight slashes nets you higher combos during training.