How do I start a new village on my second iOS device?
At this time it is a little late. You will have to factory reset one of them, redownload the game and start that game with a new gamecenter ID (do not use your old one for your base, but a brand new ID). Then you will have a new account. You can switch between the two by simply changing your Gamecenter ID from one to the other on either device. Without the factory reset, it will always default you back to your "original" base, even with a new gamcenter ID.