The goods are rare and valuable commodities. There are many goods in the game, and they become available only gradually through the ages. Every now and then you get goods as quest rewards, but usually you have to build a corresponding goods building and then grant production orders. However, neither the building nor production are cheap, and therefore this is really only worth it with the appropriate deposits on the continent map. You will never have access to all raw materials, so you trade for the goods you need in the market as best as you can. You need goods to peacefully trade sectors on the continent map, and to unlock technologies. No good is superfluous – over time you will need to use each of them.