[Lord of Angmar]

I believe that Sauron had to make the ring to rule the world. Otherwise he never would have corrupted the kingdoms of man.

I disagree. As Annatar Lord of Gifts, Sauron was able to trick many Elves into working with him. Why not continue under this guise in order to corrupt Men and trick them into servitude, instead of (unsuccessfully) trying to gain dominion over all the peoples of Middle Earth with a Ring?