To be from our city-state you have to be born here, be male or female, and have graduated from trade school. Interacting with other city-states is possible through trading useful crops and sea life. Although, other city-states have the ability to trade with us as well, we only use them for useful resources, such as Elysium is one of our allies due to its ware fare; whereas others aren't due to their lack of resources that are beneficial.