I'm creating a planet. These are the characteristics:
GEOGRAPHY AND GEOLOGY
The planet has a greater density and a gravity acceleration of 1.5 Earth-g, or 14.81 m/s2. There are two polar oceans, quite salted, the northern is inhabited by algae and small and big fish (though the biodiversity is quite limited). There are more metals and heavier stones and a lot of titania (so it can have oxygen in the atmosphere without needing to have indigenous life). Near the oceans there are places called karcas which look quite like Mars but have more metals and big craters than the other places on Wotan.
I haven't really developed it, but a planet's day last 28-30 Earth days. The inclination of Wotan is very small, so its seasons are very similar. The stellar flux is 1.13, and the planet's temperature comes from -70°C at midnight to +80°C at midday. The atmosphere is a bit thinner, so the air isn't breathable in all the central part of Wotan. There are only a few rivers and almost no lakes, so water is accessible only near the oceans.
The biodiversity is quite limited, because all the life on the planet comes from the Earth (through it is very modified). All the life (except humans) was exposed to a process of genetic engineering, so it keeps having big differences. But there are fish, algae, some mammals and some (a very few) reptiles, almost no insects.
The population is about 250.000-300.000. Half/two third lives in villages (700-1400 for each) near the ocean. The others in tribes (50-500 for each). The society is matriarchal, and the unit of the society is the tribe or the village (a family don't usually have strong bonds, boys leave the tribe or the village when they're 16-20 years old). The tribes travel for many (Earth) days, so the contacts are not continuous. The tribes usually collect the food at the beginning and at the end of journeys, but not during the trips. The main value is the life, there haven't been wars or serious conflicts.
There are a few technologies, only radios, x-rays and cleaners for salted water and a few others. The theorical knowledge is higher than the practical knowledge because they inherited it from their forefathers (it was saved because it was included in a religion that transmitted the history and the religion of the people). There isn't much interest in developing technologies. There is a small secret group/society that conserves (and develop) technologies and makes them slowly known to the others. However, it can't do much.
How would commerce develop in a world like this? What kind of money/barter/medium of exchange would be used?