Economics is not about money; it is about resources. Everyone should study at least the basics, even though many would find it boring. However, if you are a writer and building a world, it is even more important that you know something about this subject. Here's why:
As noted, economics is about resources, and their efficient use. Your fictional world has resources, so you should probably know what they are and who has them. There are natural resources, labor resources, and even intellectual resources (knowledge, skills, beliefs). Many historical conflicts are based on imbalances of resources and how people react to those imbalances.
Resources are also tied to political power. Those who control resources tend to control everything else. Just look at the power that large advertisers have in our real world. In your fictional world, this is likely to be true as well. Think about the good guys in your world and what they have. How does that compare to what the bad guys have? Is that a motivating factor for one side or the other?
Example: My World
I've been writing short stories and snippets of history for a fictional world for many years now. It is a well developed history for a fantasy world that has been used more for my mental exercise than anything else. I really should get around to publishing some of it some day. For now, though, it makes a good example of the effect of economics in a fictional world.
In my world, which has a dark-ages level of technology, there are tall mountains in the west that act as a natural barrier for most people. There are people who live there and produce metal from mines. They sell this metal to the farmers who live in the plains just to the east of them.
The farmers only have grain and some livestock to trade for the metal, but only a small amount because they are not very productive. To make matters worse, the Bad Guys live just to the south of them and often raid the farms for food and whatever else they can find. Note that the Bad Guys consider the farmers to be among the food items.
To the southwest, there is a forested area populated by a people called Lovelos. These people produce fruit and nuts for food and try to trade for other things. They are cut off from the grain farmers by the mountains and the Bad Guys. However, they do trade food to the mountain people for metals.
The Lovelos also have a sea coast that lets them circumvent the Bad Guys' territory to the south and reach the fisher folk who live in the south east and south central shores of the continent. Because the fisher folk only fish, they have a Comparative Advantage (economics term) that means the Lovelos do not have to develop their fishing skill so much and can focus on their forests and fighting the Bad Guys. This gives the fisher folk access to fruits, nuts, and lumber.
All of this trade affects who can interact with whom, so it affects the spread of news, cooperation in the war, and who eats what. As an example, if a person from the fisher folk encounters a Lovelo, there would be an inclination to trust. However, a farmer from the plains would have little interaction with Lovelos and be less inclined to trust them. The fisher folk would know of the mountain people, but only get second-hand metal through trade with Lovelos or farmers.
Should the Bad Guys ever be defeated (no spoilers), there would be many story opportunities related to the establishment of trade routes and the effects of social interaction. Who would control those lands? Who would manage the natural resources there? These are sources for conflict and conflicts are sources for stories.
In my study of economics, I found that most people think the topic is boring. I get that; it's not everybody's cup of tea. Even so, if you are building worlds of your own, you should consider doing a least a little reading. The specific sub-topic is Macroeconomics, which focuses on large systems, such as nations and states.
Note: My undergraduate degree was in computer science, but I loved my economics classes, so I started grad school in an economics program. The math was really intense and, though I loved every headachy minute of it, I decided that I was lazy. I decided to make use of my Absolute Advantage in computing (which is easy for me) and switched back to computer science.