Remember that you can only use Qi coins, which you can either convert from regular money at a 10:1 ratio, or win them through slots or CalicoJack. These are the items you buy in the Casino.
In the upper right corner of the room, there’s a machine for exchanging Qi coins, as well as a person next to a potted plant who offers to sell Statue of Endless Fortune for 1,000,000g.