You really need to work on your palette management. Lots of unnecessary colors; this could easily be done in 16.
For the robe, and clothes in general, the only thing you can do is practice. You see the words around here all the time: break out the paper and pencil. Get some reference. Do studies until you understand a good deal of what is happening. My edit is far from perfect, but takes it at least half way to where it needs to be.
For the hands: this is a hard pose, and you actually did a decent job at them. Think about each finger as a series of blocky cylindrical forms. Also, think more about how light hits form, and any cast shadows it may produce.
