How do I use game tickets?
Solution 1:
If you tap "shop" and then scroll down, you'll see "Miitomo Drop". You're able to drop a Mii and whatever it stops on is your prize. There are numerous options with different rewards, but they all seem to have limited time windows for playing. You can play with either game tickets (1 game ticket per drop) or coins (amount per drop is listed for each "board", right now they're all 500 coins).