It is recommended to wear ring or rings on the right hand or both hands but not to leave the right hand with out ring. Obviously, ring for man must not be from gold because wearing gold is forbidden for men.
It is Makrouh (disliked) to wear any ring in any of these three figures: palm, index and middle. We have narrations that wearing rings in any of these three fingered was practiced by enemies of the Prophets e.g. people of Nooh and Lut.