Before you learn the value of your doll, you must first establish what doll you have. You can find a book to help you identify your doll. There are a lot of books about old dolls that will help in your research. You can use an older book to determine your doll. However, older books will not reflect the current value. Try visiting your library. They may have a wide variety of books on the topic. One book may not be enough.
Amazon offers a wealth of books on antique and vintage dolls so shop around there. If you are only looking for an I.D., you can use an older book so may find a cheap or used one.
"Doll Values: Antique to Modern" 13th Edition by Linda Edward is a 2017 edition so should help you identify your doll as well as help you learn the current value.