In what ways is Gatsby careless, selfish or reckless?

Gatsby is careless and reckless when he gives lavish parties at his home and lets anyone enter, mostly people he doesn't even know. He serves alcohol (which is illegal due to prohibition) and generally doesn’t even attend his own parties, so he has no idea what the people are doing. Nick discovers a stranger in Gatsby's library, indicating that party guests have the entire run of the house and could steal or break anything. It's careless and reckless to let drinking strangers run all over your property every Friday night.

Gatsby is selfish and careless because he consumes relentlessly with no thought of those in need. He has "two hulking patent cabinets" which hold masses of suits, ties, dressing gowns, and shirts (the shirts that he throws down on Daisy, causing her to cry because, she says, she's never seen such beautiful shirts). Meanwhile, in the valley of ashes, people like George Wilson struggle to get by. Gatsby passes these poor people every time he drives to or from the city. He also comes from a poor family. There are so many people who could benefit from his help, but he lavishly spends his money on clothes imported from England and an orchestra, alcohol, and piles of lemons and oranges for his weekly parties.

Near the end of the novel, Gatsby is careless and reckless when he lets Tom drive his car into the city and Daisy drive it back. Gatsby has no way of knowing that letting Tom drive his car past the Wilsons' garage will lead to Myrtle's death, but it is reckless to let someone else drive your car. It is certainly reckless behavior when he lets Daisy, who is by this time hysterical and possibly drunk, drive the car back. Daisy is at the wheel when the car runs over and kills Myrtle Wilson.

Gatsby is even reckless and careless in the way he earns his money. It's not explicit but it's pretty obvious that he bootlegs alcohol, which is illegal in the setting of the novel. Hanging around with unsavory characters like Meyer Wolfshiem and engaging in illegal activities are certainly reckless and careless behaviors. This is perhaps one reason that Daisy chooses Tom in the end; although she loves Gatsby and Tom is a cheater who only breaks her heart, as Tom points out, Gatsby is a law-breaker. Perhaps Daisy feels that if she chooses Gatsby, she'll eventually go down with him. 

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