In the first episode, we are told that teenager Dexter Green is known as one of the best caddies at the Sherry Island Golf Club. From this, we can infer that he spends his days in the company of wealthy golfers enjoying everything that the club has to offer.

Dexter's own background, in contrast to the people he works for, is very middle-class. His father owns a grocery store in Black Bear Lake, which means that his family is nowhere near the same league as the wealthy golfers with whom he spends his days.

It seems that Dexter does the best possible thing with his dissatisfaction with his family's financial position—he uses it as inspiration to propel himself forward and make something of his life as an adult. When we pick up Dexter's story in the second episode, he is a self-made businessman running a chain of specialized laundries. He is now one of the men playing golf, while other young teenagers work as his caddies.

By the third episode, he is able to reveal to Judy that he could be the richest man of his age in the whole region.

Through dedication and hard work, Dexter goes from being the child of a middle-class family to being a self-made man with the resources to enjoy all the finer things in life.

One gets the distinct impression that Dexter is deeply dissatisfied with his family's social status. Solidly and respectably middle-class though they may be, they're not on the same level as the super-wealthy elite for whom Dexter caddies at upscale country club. And this bugs him an awful lot.

Dexter is restless and full of ambition. He wants to make it big in the business world and have the kind of wealth that success in business can often bring. It's not enough for him to associate with "glittering people"; he wants the "glittering things" themselves: the trappings of wealth and success.

It would be inaccurate, not to say unfair, to describe Dexter as a snob. It's not elite society that he craves, but their level of income. And he's determined to achieve that level of income in the good old-fashioned middle-class way: by working hard for it.

While rich men's sons are peddling bonds on Wall Street, Dexter's investing in a laundry business. Before long, the business takes off, and Dexter starts making some serious money. So although Dexter may appear dissatisfied with his social status, ironically it's served him in good stead. Starting out middle-class provided him with the solid work ethic that's helped him to achieve success in business.

We learn that Dexter's family is not old money. His father owns only the "second best" grocery store in a small resort town in Minnesota—and it is not the grocery the rich people patronize. We learn that Dexter's mother is a lower-class Eastern European (Czech) immigrant, which at least suggests that his father comes from a similar background:

His mother’s name had been Krimslich. She was a Bohemian of the peasant class and she had talked broken English to the end of her days. 

Dexter may not absolutely need the $30 a month he earns as a caddy, but when he decides to quit:

The enormity of his decision frightened him. He was a favorite caddy, and the thirty dollars a month he earned through the summer were not to be made elsewhere around the lake.

His father is prosperous enough to send him to the state university, but Dexter goes to the more expensive prestigious East Coast school. How he pays the difference, we don't know, but we later learn he couldn't afford to go to prom while he was there. After he graduates, Dexter needs a loan to get started and makes his money in a less-than-elite way:

Dexter borrowed a thousand dollars on his college degree and his confident mouth, and bought a partnership in a laundry.

Dexter does very well financially, but is always conscious that his class background—the child of middle-class immigrants with no social connections—puts him at a disadvantage in his new life. He realizes he can't, for example, be careless about what he wears—but he knows his children, growing up with money, will be able to. Dexter is a self-made man who always carries a sense that he does not quite belong in the world of the wealthy. 

Dexter's family is solidly middle class as his father owns the "second best" grocery store in their town of Black Bear, Minnesota.

Because his father has a lucrative business, Dexter caddies at the Sherry Island Golf Club merely for pocket money, unlike the other caddies who are so poor that they live in one-room houses. At the country club, Dexter Green is able to associate with the wealthy. There he delights in the "admiring crowd" of men such as Mr. Mortimer Jones, a prosperous member and owner of a coveted Pierce-Arrow automobile, who watches with amazement when Dexter gives exhibitions of his skillful and showy dives off the springboard of the club raft.

Later on, Dexter's father prospers enough that he is able to pay his son's way to the state university, but Dexter wants more. Whereas his father may have "association with glittering things," Dexter desires the "glittering things" themselves. That is, he aspires to the upper class rank himself in order to fulfill his desire for a perfect life. In Dexter's imagination the rich hold a magical quality which he wishes to possess. For this reason, he does not attend the state school; instead, Dexter enrolls in a prestigious school in the East where he can be associated with the denizens of his "winter dreams."