I love quilts from old shirts. They are the coziest and hardiest too, as the shirt fabrics usually have high thread count. I have made 3 or 4 big quilts from old shirts.
I often buy an article of clothing from a thrift shop or rummage sale if it has good fabric, like a cotton skirt in a print I like. Or if it has nice buttons I can take off and use on new shirts I make. I will take the clothing apart to get the good fabric it's made of, for quilting.