Why does Elizabeth dislike Darcy at first?

He insults her at a ball and she believes Wickham's lies

How does Darcy help the Bennets?

He secretly arranges Lydia and Wickham's marriage

Women of their class had few other ways to secure their future

Mr and Mrs Bennet have five daughters and no son, so their house will pass to a cousin, Mr Collins. Mrs Bennet wants her daughters married well.
Wealthy Mr Bingley falls for Jane Bennet. His proud friend Mr Darcy insults Elizabeth at a ball, and she believes Wickham's lies about him.
Elizabeth refuses Mr Collins, who marries her friend Charlotte Lucas. She also refuses Darcy's first proposal. His letter then reveals the truth about Wickham.
Lydia runs away with Wickham. Darcy secretly arranges their marriage to save the family's reputation. Elizabeth's view of him changes, and she accepts his second proposal; Jane marries Bingley.

Pride and prejudice, marriage, class, money, reputation, and women's position in society.
Published in 1813, in the Regency period. Women from the gentry could not work in professions and often could not inherit property, so marriage decided their future.

Austen uses irony and free indirect discourse, letting us see Elizabeth's thoughts while keeping a witty, critical narrator.

Who will inherit the Bennets' house?: Mr Collins: The estate is entailed to the male heir.
Why does Elizabeth dislike Darcy at first?: He insults her at a ball and she believes Wickham's lies: Her prejudice matches his pride.
Who does Charlotte Lucas marry?: Mr Collins: She marries for security, not love.
What does Darcy's letter reveal?: The truth about Wickham: Elizabeth begins to see her own prejudice.
Who does Lydia run away with?: Wickham: It threatens the family's reputation.
How does Darcy help the Bennets?: He secretly arranges Lydia and Wickham's marriage: Elizabeth learns of it later.
When was Pride and Prejudice published?: 1813: It is set in the Regency period.
Why was marriage so important for the Bennet sisters?: Women of their class had few other ways to secure their future: The entail makes it more urgent.