What you are trying is called compressing wrinkles and, as the name suggest, they are folds and wrinkles that emerge when a cloth is compressed, pretty common in sweaters, and they usually are not linear as your drawing but rather the wrinkles seem to form a zig zag pattern. I think you did it well, the problem is that the wrinkles only seems to show from one side instead of being all over the arm.
Learn how anchor points work. Here the shoulder is an anchor point, the cloth on the shoulder is stretched therefor should have almost no wrinkles, The armpit is compacted so most wrinkles happen there. Then there is the various types of wrinkles, like brides, twists, ditches, study those. Then there is the fabric of the clothing, too much wrinkles suggests that it's soft and silky, big chunks and a small number of wrinkles suggest it has a fatter fabric, which is what you need here. Look up tutorials, i couldn't figure it out on my own until i looked up tutorials and then it became really simple and logical.
I want to add that I feel that hoodie and the other hoodie? are too circular or tthe way you shaded it at least makes it look like it's a round plasticy object. With that said, I don't know how I would make it better, but there's something else you can improve on.
