>>45748237I think the best distribution would be:
>2 pokémon1st gym
>3 pokémon2nd and 3rd gym
>4 pokémon4th, 5th, 6th gym
>5 pokémon7th, 8th and elite four (only if you are able to battle them in whichever order you prefer, if not only the first 2 go here)
>6 pokémonrest of the elite four, champion, final battle with rivals
The 6 pokémon trainers should always have a region-gimmick mon (so a mega in gen 6, a Pokémon-Specific Z Crystal in gen 7 or a Gigantamax in gen 8)