what does the following quote mean? (explain)

LIZA. No: I don't want no gold and no diamonds. I'm a good girl, I am. [She sits down again, with an attempt at dignity]. (2.145)

Also could you please expand on the idea of Throughout the play, Eliza insists that she does not want the usual things: gold, diamonds, fancy dresses. She wants to maintain her dignity and achieve her original goal.