Tom Buchanan represents the wealthy, jaded, shallow, and morally corrupt of the Jazz Age. Indeed, it is symbolic that his indiscretions with Mrytle Wilson are conducted in the Valley of Ashes where the industrial waste products of New York are taken.
Tom's character is very well established in the first chapter. He is wealthy, arrogant, condescending, unfaithful to his wife, and really not very smart. Tom tries to discuss a book he has read recently (Daisy is amazed he has actually read a book), and his comments show that he doesn't understand it particularly well. This incident with Tom's discussing the book also shows he is racist in his attitudes toward the superiority of the white race. There are also passages in the first chapter that indicate that there is a hard cruelty in Tom. Tom is introduced in the novel as an example of the arrogant rich, born with money and shaped by it in developing a sense of complete selfishness and entitlement.
Based on what Nick says in chapter one, Tom seems a likely candidate to be identified with the athletes thought of in the famous poem, "To an Athlete Dying Young." Nick seems to think Tom spends his life trying to recapture past glory from his football days. We do know from Nick (again, through Nick's eyes, though), that Tom has no problem with people seeing how wealthy he is.
Tom appears to be a person who lives in the past and has trouble dealing with the present. In viewing other people, he only sees a poorly reflective self through his own eyes and is probably clouded by the life that he has led up to now.