It becomes clear that when Nick leaves Tom and Daisy that he is fundamentally "different."  At different points throughout the time he spends with them, Nick feels out of place because his values are fundamentally different from theirs.  The interactions that Nick has had with Tom and Daisy have revolved around wealth, power, and using people as means to an ends. When Nick has to tell the that he "is poor," it is a confirmation that while he might be related to Daisy, they are fundamentally different.  This is evident as Nick reflects about his experience:

Their interest rather touched me and made them less remotely rich — nevertheless, I was confused and a little disgusted as I drove away. It seemed to me that the thing for Daisy to do was to rush out of the house, child in arms — but apparently there were no such intentions in her head. As for Tom, the fact that he “had some woman in New York.” was really less surprising than that he had been depressed by a book. Something was making him nibble at the edge of stale ideas as if his sturdy physical egotism no longer nourished his peremptory heart.

Nick's values are ones that are closely aligned to his father's in the opening of the book.  Nick is not capable of the "cut throat" and manipulative mentality that dominates the Toms, Daisys, and Jordan Bakers of the world.  Nick values some type of fidelity in relationships, which is why he is put off by the idea that Tom has "some woman in New York."  Nick also believes that Daisy should be out of this emotional toxicity, reflective in how he reacts to her ornate and overdramatic declarations and that she does not "rush out of the house."  Finally. Nick values a sense of solidity and coherency within individuals.  The fact that he is bothered or put off by how Tom is so driven with a book  (Goddard's The Rise of the Colored Empires) reflects that Nick values a sense of coherency in thought and reasoned analysis.  His values demonstrate a propensity to view people as ends in their own rights, as opposed to a means to an ends, something that Tom, Daisy, and Jordan so easily embrace.  

In The Great Gatsby, this entire scene has an unreal atmosphere about it for Nick.  When he enters the house through a high hallway the windows gleam white and the grass outside seems to grow into the house, and the wind blows curtains and blows the women's dresses, and the women appear to float above the couch.  This has the feeling of illusion, which, of course, Nick discovers the relationship between Tom and Daisy is. 

From Nick's entrance into the house, until the time he leaves, Nick is a bit dazed and confused.  Notice that he is always a little behind the others, without knowledge that they possess. 

Jordan acts like he isn't even there, and of course he doesn't even know who she is.  The others talk about Jordan's career while Nick stands by unknowing.  Tom has a new book full of stale ideas to share.  Tom gets a phone call and the women know who the caller is and what the call is about, while Nick doesn't.  

The atmosphere and the personalities and details involved, combine to create a bit of a surreal experience for Nick. 

It's no wonder he leaves feeling "confused and a little disgusted." 

Concerning his values, Nick obviously is bothered by Tom's infidelity, as well as his openness about it.  The fact that the girls know about it and the situation just festers also bothers Nick.  He is also bothered by Jordan, at least at first.  She seems uppity and a bit lazy to Nick. 

The inference is that Nick brings his Midwestern values to his narration, and the ways of these easterners bother him.

Of course, at the same time, Nick is an unreliable narrator, so a reader should avoid blindly accepting his value judgments.

This happens in Chapter 1.  To me, what this shows about Nick Carraway's values is that he believes in traditional values with regard to marriage and the way that married people should behave.  In this book, Nick represents Middle America (the eNotes study guide calls him the "moral center" of the book) and its values as opposed to the more liberal East Coast values that we see in people like Daisy.

So Nick is disgusted by Tom and Daisy's marriage because he expects them to care more for each other the way married people should, according to traditional values.