My strategy for Amaria, if it can even be called one, was to use a Shedinja and a Dry Skin Heliolisk (This was in singles). Shedinja was only able to be killed by Wishiwashi, so when it came in I switched to Heliolisk, which killed it with Parabolic charge. I wouldn’t recommend this ‘strategy’ unless you really wanted to get on with the story, as it’s really cheap.