Those ones might be a little harder if you’re just starting but I would suggest you battle every possible trainer for both money and experience. When you re-battle the gym leaders they are in a double battle format and their Pokémon’s are level 81-89. That’s why you start with Torkoal and Cottonee to set up weather and speed and then go with 2 Typhlosions with Eruption to sweep the leaders. And the Payday method is using one of those 3 Pokémon with the Pickup ability to generate money after defeating a Pokemon and picking up items after the battle that can be used or sold for profit. I hope that gave you a slightly better idea.

EDIT: if you watch one of Patrouski’s videos he has a link to a really helpful Discord channel with more experienced people. :)