I would go with a Minor league Poison type Gym in Galar and work my way up to a Major League spot. Similair like Klara/Avery from the DLC but more nicer

I'd be a Psychic type gym leader in Galar.

Ghost and idk where

Id be a psychic gym leader in Galar too! I live in the uk and psychic is my FAVOURITE type

In Sinnoh probably. And I wouldn't want to be specializing in a specific type.

I'd like the gym match to be a 3 vs 3 pokemon battle in which I can use any 3 types of mon. That way the trainer has no idea what to expect.

I would also have to be good in handling all diff types of pokemon.

Id be a dark gym leader in kanto

I would do fairy in kalos

Electric in Galar

Psychic type, my character is from Kalos and originally was going to be a Hoenn gym leader, but became a trainer in a new region with new leaders and elite four (the types in order are grass, water, electric, ice, fire, dark, psychic, dragon, steel, fairy, fighting, ground and ghost). There are two teams, depending on the time, one is active 6:00 - 17:59, second is 18:00 - 5:59. The day team is Metagross, Slowking, Wobbuffet, Espeon, Mr. Mime and Gardevoir (ace), night team is Metagross, Alakazam, Meowstic (m), Gothitelle, Indeedee (f) and Gardevoir. I know none of gym leaders has a full team, but I just made the post game rematch teams first and then just reduced them for the first fight version.

Totally air in Kanto, Braviary and Kilowatteral as my Aces