this looks good so far, for shading I would recommend hue shifting (basically what enfyys said)
also for the flannel- personally I find this way easier to do and it is a bit more pleasing to the eyes at least in my opinion it’s up to you and your preference
i would use how you did the fannel for more plaid patterns for smaller clothes like a skirt or smth
also I’d recommend using over lay more for the sleeves in particular- mostly to add more depth (might not be the right word) unless you want it to appear skin tight (I dunno if this makes sense)
also find inspiration from other skinners whose styles you like and learn form those
also do reshade contest (this is more of a tip but blah) they can help learn more designs imo
hope this helps (sorry it’s long the way I type is bleh)

really cool skin! when shading / adding shadows, make sure the shadows are cooler (usually more purple) than the original colour, eg pink would go to purple not red, green would go to blue not yellow, etc. there are ofc exceptions to this rule, like often yellow darkens to an orange shade and not a green one, but unless you are taking ✨creative liberties✨ darkening towards purple is a good idea

You have good A7X tastes. The pattern of the flannel gets a bit repetitititititibve, but overall it's great! I love how yo used aklyers layerrsu