Before I started playing Elite: Dangerous I hit a few newbie guides so I'd get a sense of what to do. This site suggested:
First, you need to find a commodity with Medium to High supply at the station you are docked at. Then you should check your Galactic map to see which Stations in your jump range offer decent prices for that commodity. You can check this by going into your Galaxy Map and heading over to your VIEW tab.
Next, make sure you select the Commodity you are looking for. For this instance, we want to sell H.E. Suits, so we select them in the Technology dropdown. Through this, we can see that a station in the Dahan system is within our jump range, and they will purchase our H.E. Suits for a decent price.
However, I tried doing that and I can't make heads of tails of the lines on the map. I followed the line to what I thought it was telling me was a station that would buy them for a decent price, and ended up at just another station selling them for the price I'd bought them at.
How do I actually read the Galaxy Map's View Tab?
Best Answer
If you're trying to sell a specific commodity, the "exported to" system list in the commodities screen of the station services is a good start, but here's what I do to locate better info:
The same basic technique works well for searching for where to buy a specific commodity, such as when you have a mission.
In the example of H.E. Suits, those are imported by pretty much every economy except agriculture (maybe also not service and tourist?), and they're produced in high-tech systems.
Alternately, you can skip all of that, go to Thrudd's Elite Dangerous Trading Tool, an do Search/Commodity/Station Buying and put in your commodity, station, etc and see what price different stations were buying it for in the last couple of days.
Other trade tools: