Transportation

You might not think how many people rely on the simple moving of people or goods, but there are tons of individuals specializing in various aspects of making it happen.
First you need some goods and demand for it, lets say that there is an amazing type of tomato on a remote island. Then there are people who are willing to pay premium price for it.
Now you have a demand need to calculate if you can transport it with a profit.
You need a boat, if you have it already then you can skip this step, but in other case you need to rent it or make an order for long-term operation.
If you rent, you might already have a crew assigned to it, if not though, you need to hire trustworthy seamen and sometimes even guards if the voyage is littered with pirates just waiting for an easy target.
The same goes for any over-land transportation, there might be bandits waiting for an unguarded caravan.
After that you need to make a deal with the local tomato farmer for a steady supply of this profitable fruit.
Following, you need to create or rent out a selling spot, unless the demand is so high that it sells right from the ship at the docks.
After that you can calculate the profits and pay for everything: rented ship, tomatoes, crew, supplies for the travel, clerk at the stand, if you are lucky something will stay in your pocket.
Depending on the scale of operation, there might be multiple ships sailing back and forth with the goods, creating jobs for hundreds of people involved and that goes for importing and exporting goods, usually you do not want to sail empty so you maximize the travels.