I think the shadows in the eyes could be warmer. Play around with warm and cool colors. Even though the skin is orange, you can still play around with warm and cool colors. Check out this sketch by scott burdick. Every good artist does that.

@Adam H you got it Adam. Our vision has two basic cones. One is foveal cone and another peripheral cone. Foveal is around 2-3 inches in arms length and the rest is peripheral. Foveal cone is where we see the sharpest without distortion and the rest is slightly blurry. Which is why we see our mistakes clearly in our drawing, when stepping back enough so as so the drawing is around 2 to 3 inches in arms length. Also, it helps us reduce our drawings into major shapes and value masses. Drawing thumbnails, thus, helps with composition and stepping few feet away helps us see the big shapes and value masses. Taking breaks and looking away for a while then looking at your work also refreshes our eye to see our mistakes.

I think those exercises are more than enough. Beyond that is unnecessary. After the warm ups though, drawing what you aspire to draw is also very nice. Let me explain it, lets say, you've always wanted to draw female figures and you have an image in your mind, a pose in a setting or sth, so just draw it then once you've drawn, you will realize where you struggle then go find an image reference and draw from the reference. This kind of practice has proven to be very very very very very effective and I highly recommend it. Also, don't forget to time your drawings and have a journal where you keep track of how many hours you've put in practice.

@Jonathan Musso welcome. There is no such thing as "ready". It's a false hope. Have you ever been ready for anything in your life, truely, except for may be a job interview or school exams, :) not really right. So, yeah, the whole idea of being ready is nothing but a hopeful idea. It helps sometimes but not always. And, Drawing and painting after all is just playing, playing visually, talking in shapes and forms(well, more like poetry which is dancing with words), get my vibe? It's all fun and games, enjoy, we all love talking and drawing is just talking but visually. Have fun brother.

Amazing accuracy and execution. Hats off.

I think one thing you can clearly and quickly improve are the midtones and edges of the shadows. As the form is turning, controlling the softness of the edges of the shadows are very important and one that is easily missed.