My personal advice when dealing with communities that still don't have that many active users (like Lemmy) would be to, at least in the beginning, avoid fragmenting your communities.
Consider adding tags to the titles, I believe we might soon see apps and web interfaces that support filtering. Or make a weekly mega thread for certain content.
If you aggregate Pokémon fans but them divide them into several smaller and specific communities, the odds are those smaller ones will die out.
Just my two cents though, I never moderated anything Pokémon related so I don't know how users deal with ribbons and Nuzlocke.