I would definitely look to the characters as the formation of your paper.

Tom is stuck in the reality of a working class man who wishes his life were more like the movies. Like Tennessee Williams himself, he wants to write. He escapes the mundaneness of the real world by going to the movies, but sitting on the fire escape smoking and dreaming of a different world, a different  life, of the time when he can escape from his mother and his sister and be the man he wants to be.

Laura has a a physical disability that makes her "imperfect" although likely not as imperfect or disabled as she has become as a result of the pressures put on her by her mother, but it is clear that she is shy, insecure, and uncomfortable around people. The reality is that she is likely quite capable of living a normal life, but as she is not certain what that life is and has no role models for it she instead escapes to the fantasy world of her animals. She cares for her glass as a fragile but much-loved friend and, when the unicorn loses its horn, we see the normality that she is striving for reflected in her glass menagerie. We see that she is looking for a reality in which being broken makes you fit in instead of causing you to stand impossibly apart.

Amanda lives in the past. Reality is that she is a single mother with two grown children and no husband. She relies on her son to pay the bills and she does some work selling magazines, but she prefers to live in the past in a world of gentlemen callers. She wants to be the southern belle - taken care of by a man, any man. She holds on to the illusion of youth and to a past that no longer exists in the modern world.

You should talk about the three main character and their relationship to both illusion and reality.

Tom seems to have the firmest grip on reality. He holds down a job and is the economic foundation of the family. And, although he goes to the movies a lot and craves romance and adventure, he knows well the difference between his dreams and their possible fruition in reality. He is smart enough to separate himself from his mother and his sister, and he will eventually escape from them, cruel as that may be on some level.

Laura, on the other hand, lives in a world all her own; it is a world devoid of basic reality and given over to her own illusions. She has a glass collection of tiny, delicate animals which she constantly polishes and tells herself stories about. She also plays old, worn-out phonograph records. Except for short and sweet interactions with her brother and mother, that's pretty much her life.

Amanda, the mother, is caught between being all too aware of life's harshest realities and the unreasonable belief that some gallant gentleman caller will come into her daughter's life and sweep her away, and they will live happily ever after. She also spends much of her time thinking and talking about the long-gone, privileged days of her youth.