There are Pokémon that revolve around gimmicks in every new game, but very few have had anywhere near the gimmicky impact of Gimmighoul in Pokémon Scarlet and Violet.
Not only does the little gremlin sit in a chest and make possessed trainers collect coins for it, but only one of its two forms is actually available to catch in Scarlet and Violet. This is due to an upcoming expansion to an already ongoing Pokémon Go crossover that has Gimmighoul (Roaming Form) approaching players who collect the odd coins in the real world.
Players in Paldea are stuck with chasing down the roaming variant and using it to collect coins, while Gimmighoul (Chest Form) can appear in various locations throughout the map—initially starting out as a mystery that never really clears up even after catching it. Your best bet at finding Gimmighoul is by exploring ruins scattered throughout Paldea.
And that encounter method is going to pain if you want to evolve your Gimmighoul into the golden athlete Gholdengo.
How to evolve Gimmighoul into Gholdengo using Gimmighoul Coins in Pokémon Scarlet and Violet
The Coin Entity Pokémon is an enigma, as it goes from a small little treasure gremlin to a fun-loving, friend-making snowboarder once you collect enough Gimmighoul Coins from across the region.
Gimmighoul Coins are obtained by battling and either capturing or defeating Gimmighoul (Chest Form) during your journey. You can also chase down Gimmighoul (Roaming Form) and collect coins by interacting with it if you can—though you will get significantly more from Chest Form, typically 50 Gimmighoul Coins.
Once you have collected 999 Gimmighoul Coins, all you need to do is level up your Gimmighoul and it will absorb, collect, or do something with those coins to evolve into Gholdengo since its Pokédex entry says it seems to be made up of 1,000 coins that it uses as a way to attack enemies.