The game has many different resources. Ore, food, metals, gases, etc. You can find them on planets, in cache, buy on traders or mine it (ore mining is available).
Resources can be sold for credits, they will also be needed for crafting modules and ships (the system will be added in the future).
Each resource has its own cost and volume, which it take in the hold of the ship. Some resources, such as ore, require a lot of space, and it is quite low cost, so it’s better to take a large ship with a large capacity.
Some locations produce their own product, which can be bought at a low price and sold where this product is in de-mand at a higher price. For example, the trade route Alpha Centauri -> Proxima
Also, note that some merchants do not buy certain goods (for example, a farmer does not need ammunition, he needs water and fertilizers).
What are your ideas on the trading system?