I think, at first, Jay was simply a good-looking officer who attracted Daisy's attention because he was handsome, especially in his uniform, he was an officer, and he could mingle among rich people like he was rich, too, and therefore seemed like someone with whom she could flirt and have fun. In chapter 4, we are told that Daisy and Jay met at a gathering for the officers stationed nearby in Louisville, KY. Jay had already changed his name and learned from Dan Cody how to mingle among the rich and famous, as well as how to appreciate the finer things in life. Jay didn't tell Daisy he was penniless. The two fell in love and by then, it didn't matter as much to Daisy that Jay had no money - that is until Tom Buchanan swept into town after Jay was gone overseas to war. As for Jay, he knew he wanted the good life, his goal was always to make himself a fortune and enjoy the sumptuousness of a rich life. He didn't plan to fall in love with Daisy; he just wanted what she had to give to him. In chapter 8, we learn more about how the two of them fell in love. Once he kissed Daisy, she became his focus in life - she was unattainable but all that he wanted to obtain. Daisy found it hard to resist someone who was so completely in love with her; someone who wanted her as much as Jay did. That sort of attention is hard for most people to resist. Now that Daisy and Jay have met again, his attention is once more difficult for Daisy to resist. Combine that with the fact that her husband is having an affair and isn't very attentive to her. That makes Jay's doting on her even more difficult to pass up.