He is there for him with everything. Whether is be trying to win over a girl by planning a tea party for them, or outlining a funeral for him. Even after growing a certain disdain for Gatsby, not once did he use him for his money. Even when Gatsby offers, he denies. As demonstrated, Gatsby can truly trust Nick. Just like memories, Gatsby is interpreted differently by others, and no one knows the real truth about him; only small pieces. He tells Nick the actual truth about his past, and also sincerely invites him to his parties, rather than him just showing up. Nick respects Gatsby home, while others are getting inebriated and treating his home like an amusement