To Start off you can make coins with Bronze, Tin and Gold. Place one of the 3 metals listed into a crafting table. You will get 2 coins for every 1 ingot. To get Tin you have to trade with a ToolSmith. The ToolSmith will give you a Raw Tin that has to be smelted to get a Tin ingot. The ToolSmith has to be at least an apprentice. To get bronze you have to combine 2 Tin and one copper in a crafting table, to get Bronze Unsmelted. Ones you have that you can smelt it into a Bronze ingot witch can then be turned into a coin.
I also want to say that this is my first project and it would not have been posable without MCreator.