Why did rome choose to expand from city-state to empire? what stages marked that expansion?

Well, this is a tough one since we don't know to much history from 756 BC - 300 BC but I would say around the year 300 BC Rome started to expand and took over the Italian peninsula ... (They did this for power and glory) Also After they fought with Carthage Rome really started to expand and around the year 100BC Rome controlled much of Spain, Greece, Turkey, and the northern Africa ...