Ancient Greeks had to travel a lot. In order to keep their growing population, they had to supply food. Greece didn't have the best land to grow food/travel. So they most commonly used boats to spread to other places and grow food there.
Greek terrain was very rocky, and not too good for farming. Many people would modify terrain to be able to farm. People raised many animals too.
Since the terrain in Greece wasn't the best for farming, Ancient Greeks had a strategy to colonize many new places in order to feed their growing population.
Most Greek settlements relied on trade. They traded among colonies, and with people of the mediterranean region. In the mainland, they traded olive oil and pottery for grains, timber, and metal.