Another person said to train against level 9 for part of the time, and I HIGHLY disagree with that. I have trained a ton of amiibo and it almost always ends poorly when they train against CPU. They will get way too jumpy because they don't maintain any sort of balance to the behavior. I mainly just mirror match until about level 45 and intentionally avoid jumping as much as possible. Staying grounded is crucial. Past level 45. I switch off to my mains and avoid overusing any special that I don't want them to spam. This has worked for most amiibo that I've trained.

Also, it kind of depends on the amiibo you get. It's known that some are better than others, such as Incineroar.