So Bob Ames (Mrs. Vance's cousin) doesn't get all that much stage time, but he's a pretty important minor character due to his demeanor, views, and influence on Carrie.
We find out right off the bat that this guy is a lot different from some of the other showy, appearance-obsessed guys in the novel (yes, that means you, Drouet and Hurstwood). We're told, specifically, that "[Ames] was an exceedingly genial soul, this young man, and wholly free of affectation" (32.46).
This notable absence of superficiality in Ames's character also shines through in his attitudes about wealthy people showing off their wealth. We'll all remember his critique of these types when he, Carrie, and the Vances are eating in that fancy restaurant. He confides in Carrie that "I sometimes think it is a shame for people to spend so much money this way" (32.80) and "they pay so much more than these things are worth. They put on so much show" (32.80).
As literary critics have sometimes noted, Ames sounds a lot like late nineteenth-century social critic Thorstein Veblen, who coined the term conspicuous consumption. People who engage in conspicuous consumption spend way too much money on things they don't really need, mainly to make themselves feel cooler and more powerful. Ames takes a dim view of such folly, declaring "A man doesn't need this sort of thing to be happy" (32.105). And because Ames is characterized as such a likeable, smart, "genial soul," one could argue that Sister Carrie endorses his critique of conspicuous consumption.
Of course, Ames's critique comes as an utterly novel idea to Carrie, worshipper of all things conspicuously consumable: "Carrie looked at him a moment with the faintest touch of surprise at his seriousness. He seemed to be thinking about something over which she had never pondered" (322.81).
But rather than just dismissing Ames as some crazy nut, she's actually intrigued by him. In fact, long after he's gone, she remembers what he had to say on the subject. The narrator notes, "So, too, the ideal brought into her life by Ames remained. He had gone, but here was his word that riches were not everything; that there was a great deal more in the world than she knew…" (34.2). Carrie's fascination with Ames at the end of the novel indicates that she may be capable of changing her material-obsessed ways after all.