When reading this, please realize that this is for fully human OC’s in modern times only.
No more than six Pokemon on a battle team. Why can’t people realize this? Seriously, have you ever seen anyone battle with more than six Pokemon? No? Then why are their OC’s battling with 15 freakin Pokemon a piece? It’s perfectly fine for a gym leader or professor to have a bunch of Pokemon that live with them, or for a trainer to have a ton of stored Pokemon as long as they aren’t constantly using more than six.
Starters as starters never go out of style. There are way too many fics where the OC has Pikachu or Eevee as a starter for no reason. Try to use starters as starter Pokemon (don’t give the trainer a bunch of starters or starters from foreign regions). When a new Pokemon is released before its generation (this happened with Munchlax), and is not a starter Pokemon, don’t use it as a starter until the rest are released.