Quote Originally Posted by huttj509 View Post
The gift pieces are rewards for 3 specific steps on the seasonal chain, not as end rewards for completing the season level.

On the page that requires beating a set dungeon for the season, there's other requirements that individually reward some of the set pieces.
The Specific steps are: get to lvl 70, beat Izual on a certain torment, and beatin a lvl 20 rift solo.