Know your weaknesses and how to play around them
This is self explanatory. For example, Freddy’s biggest weakness is primarina but I learned that many people on the mid ladder click moonblast first, allowing you to use blood moon. Then you endure, earth power, and maybe vacuum wave to beat out their custap berry. Tiny interactions like this can make or break this challenge.
Also fishing for crits or earth power spdef drops is not a good way to win but sometimes it’s the only way. Even if the odds are 1/1000, might as well try.