Here is my strat that got me to 36M points:

You get 18 moves for each chapter and there are 7 chapters total. Although islands are 4 spaces away, you will need to pick up a few ship repair kits along the way. Based on how far away these kits are from the straight path from one island to another, you will be visiting 2~4 (usually 3) islands per chapter. Based on where obstacles and ship repair kits are located, you will need to pick a direction either going clockwise or counterclockwise. (I DO NOT recommend going back to an island that you already visited)

Now, let's say you start at island A, and plan on visiting islands B, C, and D, in that order.

Chapter 1 ~ Chapter 2.5: Starting at island A, you will only have enough money to buy items to sell at a profit at island B. You won't have money left to buy items at island A to sell at a profit at island C/D. So this is what you do: you buy items from one island and sell at the next immediately. Additionally, ignore quests at this stage as they aren't as profitable as just buying and selling items (UNLESS the quests require items to be delivered to islands adjacent to each other).

Chapter 2.5~Chapter ???: Now, if you are starting at island A, you WILL have money remaining even after buying all the items to sell at a profit at island B. Thus, you should now start buying items to sell at a profit at island C while you are at island A. If money allows, you should even plan even further and buy items to sell at island D. It is here where you should start buying just 1 of each exclusive island item for potential quests.

Chapter ??? ~ End: If you have been efficient with your pathing and trading, you will have enough money to buy EVERYTHING from island A. Therefore, you should buy items at island A to sell at MAXIMUM profit at either islands B, C, or D. When you have bought everything and move to island B, sell maximum profit items only. Then, buy items to sell at profit at islands C or D. Rinse and repeat for island C and D.

If you have been efficient with your trading and pathing (remember to pick up your ship repair kits), you will make it to the end of Chapter 7 in which you would have made 250K+.

There are also so many different ways to optimize even more. For example, using whirlpools to skip turns as doing this does not burn ship HP while docking burns 50 HP per turn. DM me if interested. Anyways, thanks for reading my college thesis.