Clearly, in any work of literature there are any number of literary elements for you to focus on and analyse. In this great short story, one clear literary element that stands out is the description of the stockings when Mrs. Sommers first feels them:
But she went on feeling the soft, sheeny luxurious things - with both hands now, holding them up to see them glisten, and to feel them glide serpentlike through her fingers.
Note the word "serpentlike" in this description. The serpent can be said to act here as a symbol of temptation, referring to the Biblical allusion of the Garden of Eden and the way that the Serpent tempted Eve into eating the apple. In this story, this descriptive use of "serpentlike" shows the temptation that Mrs. Sommers is just about to give into, even though it is so completely out of character for her.
This is one example of a literary element in this tale. You might want to also think about how Mrs. Sommer's character is presented and the reasons behind her sudden change of character in spending the money entirely on herself and in "frivolous" ways.