What are Home Coins used for?

Home Coins are the Homeland's own currency, and you earn them by selling crops and goods to merchants. That makes the farm a loop rather than a decoration. You grow and produce, you sell, and the coins go back into seeds, production materials and farming upgrades so the next round of selling is bigger. Spend everything on eggs early and you starve the thing that generates the coins in the first place.

The spending side covers two different jobs. One is the Home itself: expanding and upgrading its production features, which is the infrastructure side of the currency. The other is output you take away with you, eggs, crafting goods and evolution materials. Evolution materials are the ones that matter most outside the Homeland, since they feed into your Aniimo rather than your plots.

Not everything is buyable this way. Upgrading an Aniimo's core skill runs on Prismatic Stones, so no amount of farming income will push that along. Treat Home Coins as the currency for growth, goods and eggs, and look elsewhere for skill progression.