The Road to Empire Begins with Equal Exchange

After taking a look, it seems to be relatively ordinary, barely enough for food. Equivalent exchange actually means that many cheap things can be exchanged for high-value things. Because human pricing is actually not in line with the value of the object itself. Ordinary stones may only need a little to exchange for a beautiful watch, because luxury goods are deliberately priced by humans, and the value of luxury goods themselves is not that high. But the protagonist of this book has not actually seen this, so he cannot take advantage of this value difference and use the entire human world to reach the sky with his left foot and his right foot.

I haven't looked at it yet and asked whether it should be a single heroine or multiple heroines.