Thanks for trying out the game! I definitely need to work on making the connections more intuitive. 2 iron (yellow) from the mine goes into the blacksmith to become weapons (purple) which is then sold in the shop. Peasants can automate the process, and be upgraded to speed things up. It's admittedly not explained due to running out of time. The gold currently has no use, but I want to add a dedicated skill tree after the game jam ends and I clean up the code. Thank you very much for the feedback!