You have to do missions and you have to know where in the map there are only a few users, meaning where everything is FULL of missions that you can do without moving.
Forget the missions about cryptos or crystals, focus on cards, crates and mining boosts, do exclusively these missions and SELL what you find in them in the market.
Doesn't even have to be a high price, make the price low enough so they sell quickly.
Regular price is something like bronze 1 sat, silver 2 sat, gold 3 sat, blue 5 sat, mining boosts 40 sat, I usually add up the stuff I'm putting on sale for these prices and then reduce the total price by about 20%.
This way I'm getting about 2000 sat per day from the market.

Note: I am aware, the site ONLY pays the amount of cryptos people get in mining and crypto missions, therefore the sum they pay is somewhat fixed and very low, whatever I make is money other users make less, meaning the more users figure this out the lower the prices in the market will become, so this isn't a permanent solution, it just works for the time being, while some users are still into the combat thing.