In The Great Gatsby, we get enough information to think we "know" most of the people who live in and around East and West Egg. Except one. The only person we never really get to know is Jay Gatsby, even though we know his original name is "Gatz" and that it seems quite reasonable to assume that he has a sort of criminal past. Gatsby's choices are limited even while he seems to be "pushy". His life choice is that money can buy happiness or at least some sort of affection. Daisy made her choice for becoming "respectable" old money years ago. Nick chose to become rich and still stay scrupulously honest on Wall Street
Gatsby came into his money in not necessarily "legal" means. Gatsby is what is usually referred to as "nouveau riche." His life choice is to be like the old-money rich. However, it just cannot happen. He can never be really accepted by the citizens of East Egg. It is reminiscent of "nerds" trying to hard to join a fraternity or Jews wanting to become members of some exclusive club. In the 1920s and 30's the social divide in America was almost as rigorous as that in royal Great Britain.
Daisy is a snob. However otherwise like-able she may be, she just wouldn't be caught dead going to parties in the nouveau riche mansions of West Egg. The Buchanans, Daisy's in-laws, are prime examples that there is more involved in "Egg" society than having money. It's how you make it. Daisy was one of those Southern belles, a debutante who first met Jay Gatsby when she was still a teen-ager, and he started his lying about his own background in trying to woo and win Daisy. She was upwardly mobile, so to speak, and selected Tom Buchanan. "Select" is properly the accurate word. Love is not really Daisy's specialty. She even tends to ignore her own baby daughter. She wants to be, and fairly much is "comfortable." And, even though some old romantic moments may have surfaced when she and Gatsby meet again, Jay has no c...