First, Silvique: its most obvious export is lumber, but there are several other things it might trade. For instance, those hills might be loaded with coal. The areas near the southwestern coast would have a very mild climate, and would be good for growing sugar, spices, or cotton. I expect fish from this region to be locally traded a lot as well. The northeastern coast/plains are where we're most likely to see traditional European farm animals like cows or pigs.
Geshi, being primarily mountains, probably survives on a diet consisting mostly of fish from the western coast. That coast is probably the "bread basket" region of Geshi, with rice or potatoes grown on terraces like in the Andes. The rest of the land would probably be more pastoral, ranching wooly animals like sheep, goats, or yak.
Finally, there's Fer. Being all desert, water is the lifeblood of Fer, and all the cities will situated on sources of it. Fish from the warmwater current would probably supply a lot of food, the the biggest source will probably be along a regularly-flooding river like the Nile. Just as in the Roman Empire, this food will probably be exported- along with luxuries like ivory and rare animals (elephants, lions etc). Other than that, there's unsurprisingly little of value in the desert.
Trade would probably occur mainly in a clockwise direction on the inner sea, following the main currents. This sea is likely shallower than the Mediterranean, so it's a good place for oysters and coral. And also the sea snails which gave the famous Royal Purple
worn by kings and emperors.