Throughout my run, stat based moves helped me a lot. Mostly Trick Room, Confuse Ray, Screech, Nasty Plot and Toxic. I don't really follow a specific strategy. I just keep soft-resting until I win. I struggled a lot with Shelly and Titania. I was able to win against Shelly by luck to be honest. Psybeam confused a lot of her Pokemons, and they all hit themselves. As for Titania, I won because of Gigalith's sturdy ability. Other gym leaders were not as difficult.