If you're designing a Fakemon dex, try to avoid these:
A) Don't come up with a bunch of legendaries. You can come up with a "Major legendary" and a trio of "sub legendaries". Remember, they're supposed to be part of a legend, so try to put small hints about them on key parts of the region.
B) Try to add "normal" fakemon, both physically and on stats. By physically i mean, think of Rattatas, Pidgeys, Sentrets, Wurmples, and HootHoot's. Simple and small. It's kind of strange to find this mystic enigmatic glowing Fox of fire on route one, for example. Then, as you go on in the game, as the difficulty level grows, cooler looking Fakémon should appear.