For a mercantilist economy, the best kind of trade was trade with your own colony.
In a mercantilist system, a country amasses wealth by:
Mercantilism grew in popularity in the 16th and 17th centuries when European powers established colonies outside Europe. By only enabling their colonies to produce raw materials and trade with their mother country, these nations could create manufactured products to sell for profit. The colonies were therefore necessary for wealth creation, and they were banned from representing any competition because they couldn't trade with foreign powers.
Great Britain most benefited from this system in the mid-17th century. For example, with the Navigation Acts, American colonies could only buy products like sugar, tobacco, cotton, and iron from British merchants.