When you get the Snowcraft, hold X and press O repeatedly for about 15/20 times. A mini game will pop up in which you can earn BIG money. Of course, you could just play the game normally, but don't expect to win much.
The easy way:
Play the first round, and note down the positions of all of the cards, then cancel that round. Then start a new round, and cancel it, and do it again for 31 times. Make sure you stop after 31 times, because otherwise you'll miss the chance to win easily. One the 32nd round, the cards will be in exactly the same position as the 1st round, meaning you can win the game in less than two minutes.
You'll win: 40,000 Gil, and elixir, and a Phoenix Down. You can use this method more than once. <3