At this point, you now have your currency system that interacts with an NPC. You are able to buy items from the NPC and stock as many items as you want in your inventory, and then correctly use them. Using this knowledge, you should easily be able to create more items throughout the game using the same strategies that we covered in the last couple of chapters.
In the next chapter, we will dig deeper into useable items and work with equipping weapons and armor, which will temporarily change the stats of a player.