You've been playing Pokémon Legends Arceus for hours now and you're gradually understanding how important it is to have money in the game. First to buy resources useful for your adventure (if you don't you don't have time to farm), to obtain rare items from the merchant or even change your appearance thanks to the clothing store and the hair salon. In reality, the best way to use your Pokédollars will probably be to expand your inventory and it is very very expensive! In short, let's see now what are the main techniques to easily get money.
Sell useless items
If most of the resources you find during your exploration seem important to you to keep, others on the other hand exist only for resale. So, if you find Nuggets or Star Pieces, don't hesitate to resell them to a merchant! This will earn you thousands of Pokédollars. This is also the case for Pokéshi Dolls that you can resell without hesitation.
Crafting Star Pieces
You can craft Star Pieces and resell them like Nuggets. To unlock the crafting plan, you can buy it from Ferno in Rusti-Cité for 10,000 Pokédollars. To craft one, you will need 3 Red Shards, 3 Blue Shards, 3 Green Shards, and 1 bag of Stardust. Each Star Piece you sell will earn you 5000 Pokédollars each.
Defeat the Gatherers
A sort of Team Rocket from the old days, you'll meet these three sisters at some point in the story (Marais Crimson). But be aware that it is then possible to find them by chance in the four corners of Hisui in order to fight them again. If you manage to defeat them, they will then give you Nuggets.
Take advantage of Space-Time Distortions
If you see a Distortion appear while exploring, go for it! In addition to offering you many rare Pokémon, these rifts are filled with rare items such as Shards but also Nuggets. As you now know, these sell for 10,000 Pokédollars each. Regarding the Shards, they are very useful for making Star Pieces that you can also resell.
In short, you will have understood that it is all a question of finding Nuggets (and other resources of the kind) in order to resell them regularly. Of course, you can simply farm the money by capturing as many Pokémon as possible during your explorations and in particular Barons: during your Research Report , Professor Lavender will be very generous.
Feel free to share your own techniques for making money on the game in the comments.