Explaining that in detail would be really time consuming and redundant, as it is not THAT difficult to figure it out. Take a close look at the commodity market of every economy. Things that are on medium/high supply there are most of the time produced there. Things that are on medium/high demand are needed. Sometimes you just need to read the name or description of a certain commodity to know who will buy it. Furthermore the right window in the market tells you where the currently selected good is exported to / imported from. These export/import data can also be displayed in the galaxy map for systems in a certain distance. Combine those sources of information and you'll soon get the general idea of what to trade between certain economies.
For example if you are on a High Tech station you'll notice that plenty of the goods in the "Technology" category are in med/high stock and can be bought below galactic average. Now your eye falls on a commodity named "Land Enrichment Systems". Well... who could need that!? YES, RIGHT! The agricultural station just aroud the corner could sure make some use of that thing. You decide to buy some of them and head out right away. But wait.. if that plays out to be a profitable deal you might want to come back and get more of these Land Enrichment Systems. Now what could you haul on your way back. Obviously that would be something which is produced on the agricultural station and sold there for below average prices. So it can only be food or "legal drugs" (Tobacco/Wine/Beer/Liquor). Check if your current High Tech station has a high demand for any of these goods and is paying above average for it. As a rule of thumb: The more expensive goods tend to yield more profit/ton. So the best trading good you can get at an agricultural station is mostly tobacco. Unfortunately this is banned at many stations. So eventually you may have to stick to Coffee/Tea/Animal meat on your way back. Take a screenshot of the selling prices for these goods at your High Tech station. So you'll know which commod makes the best profit on your way back. Voila! You figured out your first trading route between a High-Tech and an Agricultural economy.
I admit.. this example is really basic and simple. But it works that way with all the economy types. Sometimes you can't just figure out your best bet only by the name of the commodity itself. But once you start trading, you'll get the hang of it and figure out the most profitable items between certain economies rather quickly.
Hope I could help.
The problem comes when there's more than one economy. I've found plenty of routes with minor profits but when it's extraction/industrial to high tech/refinery and certain commodites you expect to see are missing entirely it gets convoluted. I have a spreadsheet that tells me what commodities are in demand to and from each economy (like gold is best from extraction to industrial) but a lot of the listed commodities aren't available like it says. Go to an extraction station to buy indite or bertrandite to sell to a refinery nearby and they never have any, or a refinery to buy superconductors and they aren't even listed )unless my spreadsheet is wrong and they aren't found at refineries). Supposedly they're bought at refineries and sold to industrial and high tech. I've just never seen them for sale anywhere.
That depends on what is fetching the best profit at any given point in time
Usually the commodity on the Flagship leg of the route is a precious metal like Palladium. Palladium is produced by extraction economies and tends to be desired most by High Tech commodities. The trick is getting good profits on the other legs of the route alongside the flagship route.
Imperial Slaves can be another good commodity. Obviously those are found in Imperial Space, and you can usually find them on high population Agricultural worlds.
Fancy medicines like Performance Enchancers and Progenitor cells can also been seen fetching goods prices frequently. Usually they're desired by the population of wealthy systems. The greater the population of wealthy citizens, the greater the demand. Consequently wealthy agricultural worlds tend to have the highest demand for these medicines because Agri worlds tend to have HUUUUUUGE populations.
I didn't even know wealthy was a stat. How do you see if a world is wealthy anyway?
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