You can earn a bunch of extra money when you win Pokémon battles, if you take a few steps.

First, look for the Amulet Coin in the Paniola Ranch area. You'll find it behind the red truck that is parked near the Pokémon Nursery. Give it to your favorite Pokémon to hold, and that will double your winnings received from battles with other trainers (provided the Pokémon that is holding the amulet participates). You can also combine the effects of the amulet with the Happy Hour move, to quadruple your earnings. One easy way to obtain that move is by claiming the Mystery Gift Munchlax, which is available until January 11, 2017.