When the game first begins, it tells you to pick an element. The options are listed in a neat and tidy fashion with helpful descriptions, which can be seen here:
Everything is nice and tidy organizationally, except opposite elements are paired together. Fire/Water, Earth/Air, Life/Death, Light/Darkness, Gravity/entropy, and Time/Aether.
Make a deck using these two elements, and then I suppose I might host a tournament or something. Have fun
(Bonus points if you pick a more difficult pairing to do. Like Air Earth
)