The first 10 chapters of the this novel establish all of the themes that Austen will then elaborate on as the novel progresses.  The first line of the novel says that men of fortune much be in search of wife.  That alone establishes one of the primary themes:  marriage.  Mrs. Bennet's concern in getting any or all of her daughters married illustrates how important marriage was women in this time period.  That theme is elaborated when each of the main female characters talks about the subject.  Jane is a hopeful romantic who would like to marry for love; Charlotte is a practical woman who doesn't care about love, but is primarily concerned with financial security; Lydia and Kitty are silly romantics who are more concerned about the shallow appeal of men in general; and Elizabeth declares that she will only marry for true love. 

Another important theme that dominates the novel are the interrelated themes of pride and prejudice, thus illustrating the significance of the title of the novel.  The two main characters, Darcy and Elizabeth, both demonstrate personal pride that then makes them act and/or behave in a prejudicial manner.  Darcy is full of pride in his family name and position in society, so he has prejudices against a lower class family like the Bennets -- more for the way Mrs. Bennet and Lydia behave than anything else, but it is a complicated situation for him.  Because Elizabeth's feelings and her pride were wounded by a mean-spirited comment by Darcy, she is prejudiced against him.  This is pushed to an even greater degree by the lies that Wickham tells that completely slander Darcy's character.  This primary conflict is the what drives the plot line of the novel, but Darcy's and Elizabeth's change of heart about each other provides one of the most satisfying resolutions in literature.