Dexter Green is "newer" than the "careless" wealthy people since wealth has been unfamiliar to him and not a matter of course. He also is "new" in the sense of being somewhat naive about what wealth can really bring him.
Dexter is "stronger" because for him wealth is itself a means to a goal, but he is confident that he can attain it. On the other hand, the "careless" rich take their wealth and all that it affords them for granted. They feel no powerful need or deprivation. Once he attains his wealth through hard work and confidence, Dexter values this wealth as something that he must protect because he knows that without it, he cannot attain his goals. The "careless" wealthy often do not sense a real danger as Dexter does.
After Dexter has met the wealthy Judy Jones, who is "arrestingly beautiful," he sets his sights on becoming one of her social and economic class. Thus, he is driven to attain wealth: "...he wanted the glittering things themselves." Moreover, he is "unconsciously dictated by his winter dreams" of becoming rich. In his confidence Dexter chooses to attend a prestigious Eastern college over a state school. Eventually, he becomes a success in his own business.
But all that Dexter accomplishes is not done for the attainment of money per se. He desires wealth for a stronger purpose: the attainment of his dream of a perfect life that involves Judy Jones and her love.