Joy/Hulga's mother, Mrs. Hopewell, claims to be fond of Mrs. Freeman and her daughters. She constantly tells everyone that she has kept them for so long because they "are not trash" but "good country people." In reality, the Freemans were the only ones to apply for the job at the Hopewell farm, so this shows that social status is the most important thing to Mrs. Hopewell. Her daughter, Joy/Hulga, is also important to her, even though she does not understand her daughter and even though her daughter seems to have a great deal of contempt for her. She puts up with a lot of abuse from Joy/Hulga but she loves her, deep down, and tries to ignore her rudeness. She is also proud that Joy/Hulga has a Ph.D degree, even though she is intimidated by her daughter's education. The third thing important to her is her farm.
Mrs. Freeman is a stubborn woman who always has to be right, so this is important to her. Also, her two daughters Glynese and Carramae are important to her and she brags about them all the time, annoying Joy. It is also important to her that people think she is smart, or "quick" as she says, to appearances are important to her as well as to Mrs. Hopewell. She is not particularly fond of Joy/Hulga. Her job is also important to her.
Joy/Hulga does not seem to take any pleasure in life. She is well-educated (she has a Ph.D), but this does not seem to give her any happiness. Joy/Hulga enjoys reading, so this is important to her, and she enjoys being rude to people and showing off what she perceives is her intellectual superiority. She claims to not believe in God and enjoys throwing this up in the face of the Bible salesman, Manley Porter. The most important thing to Joy/Hulga is her wooden leg. Although it marks her as handicapped, she is really more handicapped by her soul and her attitude towards life than by having a wooden leg. She clings to the wooden leg in a perverse way and it almost becomes a symbol of who she is, how she is different. No one is allowed to touch the leg.
To Manley Porter, money is important. He claims Christian service is important to him, but he is a con-artist. Because he is cruel, he steals the one thing that is important to Joy/Hulga, her wooden leg. In so doing, he robs her and humiliates her.
There is a lot of much deeper symbolism to these characters and to Joy/Hulga's leg and what it represents, however. You can read about it here on eNotes at the link below.