1) The reason that Gatsby wants to meet Daisy at Nick's house is so that he can show her how much money he actually has. Because Nick lives so close to him, Gatsby can casually invite Daisy over to check out his home. If Gatsby invited Daisy for dinner at a restaurant, for example, it would seem random to just invite her over out of nowhere. Also, by meeting at Nick's house, Gatsby's house looks so much better compared to Nick's house. By going from worse to better, Daisy can realize how much money Gatsby actually has. Gatsby's intentions are to re-impress her, and meeting at Nick's house helps him do that
2) As Tom, Nick, Gatsby, and her many other suitors discover, Daisy’s affections cannot be relied upon. Indeed, this is precisely what makes her so desirable and frustrating to the boys. They are all hoping to be the one to finally pin her down, to be the only fellow she ever loved, to have that thrilling voice purring to them alone. She is like Lady Fate of the ancient Greeks, forever beguiling and tormenting men by giving her fortune’s wheel one more spin, bringing the lowly to the top of her affections and snatching away her riches even from kings. Or maybe she’s more like a character out of Shakespeare, who also associated his most tantalizing and changeable heroines with water and moonlight. Like Cleopatra reclining on that gilded Nile barge, Daisy knows the power of spectacle. And like Cressida, her fickleness is the stuff of legends. If I am ever false, says the wanton Trojan to her lover Troilus, just before she heads off to the Greek camp to collect kisses from the enemy, “let them say, to stick the heart of falsehood, ‘As false as Cressid.’” One might add: as false as Daisy.
Hope this helps!