The Buy More Materials is a mod that adds more items to the game and allows you to buy more of them than you were able to previously.

The items you can buy with the mod are:

Monster drops: If you're a successful farmer or rancher, you probably have a lot of monsters on your farm or ranch. They can drop a lot of loot.

Other more naturally occurring items: There are other items that you can get in the game, but they aren't as valuable as the monsters.

It is now possible to buy some resources directly from some non-shop NPCs in v1.2.

With v1.4, you'll find two new shops run by Leah and the Wizard with all sorts of goodies available.

As for v1.5, management is a lot easier since the creator can now compile the mod file automatically from the spreadsheet.