Also, resources are no longer a "you only need one" deal. When you acquire a resource through whatever means, you assign it to a specific city, and its benefits go to that city only (cities have a number of slots to accept resources that can be increased through buildings, etc.). So getting more copies of a resource lets you assign that benefit to more cities.
When you create a trade route with a foreign city, you get a copy of the resources that are being produced in that specific city. So ideally you want to create trade routes with every city you can. It's not clear what limitations there are on how many trade routes you can have.
When you create a trade route with a foreign city, you get a copy of the resources that are being produced in that specific city. So ideally you want to create trade routes with every city you can. It's not clear what limitations there are on how many trade routes you can have.