Well, here's an idea I have for you. If you look at First-Person spaceship-shooting games such as Privateer 2 (old one) or Freelancer, or even something more similar to your game's style such as Fairy Godmother Tycoon, they use news or random-generated circumstances to which affect the resources or demand for resources in their various different cities/regions. For example, you might have a type of sickness suddenly occurring in one of your islands to which will create a high demand for medicinal leaves or medicine-related goods. A city might suddenly discover a gold mine (they now have a surplus of gold) to which now their gold is much cheaper for you to buy and sell to other cities for loads of profit. A city might experience in a wave of immigrants from "Gem-Land", and because they like working on gems to make jewelry, that city's demand for gems might go up. Etc.

This would require you to implement some sort of news forecasting system in your game, to which could be like a newspaper, or Harry Potter magical bird delivery express system, etc.

Here is another thing to make trading from port to port more challenging, factor in food-upkeep of your ship, as well as the well-being of your crew (sickness, scurvy, health, entertainment). For example, ports might carry a variety of edible goods, or toys such as chess, or beer, to which you consume each time you set sail. The farther you go, the more food you would use for that trip. Additionally, the more cargo you carry, the more crew you would perhaps need to maintain it (loading it and unloading it), so your food/health/entertainment upkeep also becomes more expensive. This sort of forces players to consider how far they want to go in their trading routes.

You could have different kinds of ships that have different kinds of speeds or cargo capacities. A fast ship won't eat up your upkeep as much, but a huge ship could carry loads of things from one port to another.

If you want pirates in your game, you could also include weapons goods such as cannons, cannon balls, gunpowder, cutlasses, and things.

And while on the subject of pirates, the encountering of them could perhaps be a part of the many different random events that could occur as you sail from one port to another. Other random events could include storms, or monsters, or whirlpools, or discovering a treasure-island, etc. These could all spice up the game and improve its replayability.

Nice game you have there btw, I really like the style and the animal-people.

The concept's really intriguing. It's also my favorite design mechanic, so hopefully there's no such thing as too much feeddback!

Along with what Tangireon said about randomizers, I'd suggest:

Trade barter styles - They like to bargain a little or a lot. Perhaps you have a meter indicating how much patience they have, and how far you're into exhausting it. When it's up, they close for the day or you lose favor with them or something.

Scarcity = Value - I like the way the old game Gazillionaire Deluxe does this. You have a simple screen hinting at where things are plentiful and where they are cheap. This changes as you travel, however, and as rivals alter the supply and demand at ports. You could make this random, but I'd suggest cycles interrupted either by events or competition. I'd like it if I could make some determination based on what they have and what they need / consume. If I see someone who has lots of bread, selling bread probably isn't a good idea.

Desired Items Get Removed - I'd like to see some things disappear off the table as a sign of success. For instance, if the shopkeeper takes gems off the table, you know they REALLY wanted gems. You could turn this into a pattern, so that if they keep doing this, you know to offer more competitive trades.

Multiple Traders At One Port? - If you put in the potlatch system for social status, consider adding it on a trader basis and a community (port-wide) basis. Raising your value community-wide could be the result of special trades at critical times (medicine after a bad storm); whereas trading with a single trader and being not necessarilyl generious but fair gains you a better rep with them (at the expense of another trader in the same port who might be a rival?) I'd definitely give them different valuation levels and quantities they could tolerate, such as the merchant who pays REALLY well but only buys a handful of your goods.

Time Pressure / Item Decay - What if those apples spoiled? You could have a quality level attached to the merchandise (maybe different graphics, say browner or mushier looking apples). Even in a turn based game, turns could last a variable amount of time in order to reach different ports.

More Flavor Text + Moods - I'd like it if I entered a trading shop and the owner said, "Oh, it's YOU again. Come to swindle me out of more bricks?" Flavor text is a great low investment / high return way of making the traders stand out. You could even indicate moods using text ("Have just a moment" versus "how can I help you today?"

If you used Tangireon's idea of resource limits / needs for your ship (which I think is excellent) you could add in time as an important factor. Maybe you wait for a trader to open.

You could also really jazz up considerations for the route-- are you going with the current / tradewinds, into storm territory, pirate infested waters?



(btw, I couldn't figure out how to switch ports once I'd bought by stuff... is that in yet? I could only go to a different port by restarting.)

This makes me think of the classic Taipan, which seems to be quite similar to your idea, at least in principle.

I've never found the actual trading portion in games to be that entertaining, my first thought was perhaps a mini-puzzle like you'd see on Puzzle Pirates representing your attempt to haggle with a merchant. Various factors like supply, demand, etc. can influence it but the puzzle aspect as a front-end could make the whole thing more palatable for the player. Something like these perhaps.