Congratulations, you have successfully sold a material and bought a resource. You have completed Episode 12.
As the game continues, you should complete as many trades as possible with minor nations with whom you have Trade Consulates. Each of those trade deals improves relations between your Great Power and the Minor Nation.
You now know the two methods--transport and trade-- of gaining resources (or materials) for production. Generally you should purchase resources that are in short supply in your own country. Buying materials on the market is often a bad idea because of the high costs. It is wiser to rely on your own production to turn resources into materials.
