Style A:
Be the same character as your amiibo until it is level 30, and use omega form stages. If your amiibo has a custom move, make sure you use the custom moves too. Then use any character you want on different stages. Make sure to train them at least 5 times on a non-omega form stage and twice on a walk-off stage.
Style B:
At levels 1-10 train them with a level 9 CPU on an omega form stage. At levels 10-20 use the same character as your amiibo, and still use an omega form stage. At levels 20-50 fight them with different characters. Characters that are have a very different play style than your amiibo are recommended.
Style C:
Very similar to Style B, at levels 1-10 train them with the same character as the amiibo, and don't use a CPU unless you are worse than the CPU. At levels 10-30 battle them with different characters. When they are at levels 30-50 keep training them with different characters. If you have any other fully trained amiibo, it should fight your level 30-50 amiibo, to give it even more practice against different characters. When they are level 50 continue using different characters against them.
Is your amiibo spamming a certain attack?
Amiibo will sometimes spam the same attack. If your amiibo does, give them a 300% handicap, be Fox, and whenever they do the attack that they are repeating, hit them with your side smash. If you have trouble doing this because they have a shield ignoring attack like Bowser's side special, use Fox or Falco's side special. To do this you need to run away. (This could teach your amiibo to run away, after this round start another one with Fox or Falco and use their side special when they are running away.) Run away from your amiibo until they use the attack and then use your side special. (Tip for training Kirby amiibo, never spam your hammer or they could get into a very bad habit of running away!)
