For early in the game, with a moderate amount of gold, the best way to profit from trading is to circle through three towns: 1-Dagger Wound Islands 2-Ravenshore and 3-Alvar.
In each town, you can sell a product purchased in the previous one, as well as fill your inventory with stock to sell at the next town. Before doing this though, I suggest you acquire Nathaniel Roberts the necromancer from Shadowspire, and Ithilgore the Dragon from Garrotte Gorge.
The necromancer, once you buy him the town portal spell from a magic shop (make sure he gets to master Water Magic so he can learn it) can teleport you from one town to the other instantly. NOTE: You must have visited the main fountain once before hand during the game in the cities you wish to teleport to.
The Dragon can serve to fly from the fountains to the shops which will save you a lot of time. Once you have the dragon join you, get him up two levels, train him, give him max. points in the Dragon ability then return to the Dragon Caves so he can become a Master Dragon. This gives you the fly spell.
Here is what you can buy and sell in each town:
Dagger Wound Islands: SELL TOBERSK BRANDY, BUY TOBERSK FRUIT.
Ravenshore: SELL TOBERSK FRUIT, BUY TOBERSK BRANDY.
Alvar: SELL TOBERSK PULP, BUY TOBERSK BRANDY.
Teleporting drains mana, but this is no problem: every time you teleport to Alvar, drink from the fountain to restore you spell points.
Locations of shops:
Dagger Wound Island: In the Main Village, in one of the huts near the main hall.
Ravenshore: From the fountain, cross the small bridge to the small section of the village. It is one of the huts on your right after that bridge.
Alvar: Fly Down South East to the remote village. It's the hut next to the Inn.
Go through each town several times every time you're short on cash. Although the revenue isn't that high compared to other trades, it's a great help early in the game when you need cash to train your party and cannot afford to trade more expensive items.