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>Team must be male unless it's a female only species
>Levels must be within range of each other
>Never overlap types
>For each region, only use Pokemon that were introduced with that generation. Example: Gen 3 Pokemon only for Hoenn games, Gen 4 Pokemon only for Sinnoh, etc..
I've only broken the last rule wit Gen 6 in X. I needed a Fighting type, but the ones that were introduced in Gen 6 had secondary types overlapping with my team. In the end I had to settle for the Lucario Korrina gives you.