A lot of what I do to touch up my photos is just mess with the shadows/highlights with the burn & dodge tool on photoshop. (that's all that is done in this photo aside from the eye color change/deleting the wrinkles in the green screen)
You don't have to be super skilled in photoshop to make your pictures come to life better.
I don't have the best camera/lighting set up due to my small amount of space, so learning how to contour/highlight on photoshop has really helped me a lot with making my photos look less flat.
Idk if there is any cosplayers on here but if you guys are interested in me doing a small tutorial on this then let me know. :)