I agree with everything Darko has said above.
To study drapery, folds, wrinkles I suggest Burne Hogarth's book, Dynamic Wrinkles and Drapery, ISBN-13: 978-0823015870. It was recommended to me a few years ago and I still use it as a reference. His book is way over the top showing wrinkles and drapery, but I think it's just his teaching style. Dial it down a bit when you start applying the techniques in putty. If possible, follow up the book with a visit to an art museum that has representational or classic sculptures. See photos below. The first three are from the web and the last is from the First National Bank sculpture garden commemorating the West. Notice the teamster is leaning; see how the folds and wrinkles result from that movement and tension? What are you using/going to use for tools to make folds and wrinkles? Personally I'm still studying and learning this subject and I have a long way to go to equal the real talents on this site!
All the best,
Dan