Recently I started making my amiibo fight each other in Smash tournaments. I'm keeping a record of their wins, losses, their win/loss ratio, how many times they've come 1st, 2nd, and 3d, as well as how many times they've won a championship and how many times they've defended a championship. I have done two tourneys so far. I was going to stream the tourneys and have a betting system like TheGreatTeacher does for his BT3 CPU tourneys but I do not have a capture card and I'm not sure I'll be able to stick to streaming it consistently.
I also give each amiibo theme songs that I play in certain situations. There's no specific criteria to when I play the songs, just whenever I feel their song fits the situation or they're defending a championship.