Hey, its a good start
I have to ask, are you self taught? Nothing wrong with this! As I was initially self taught and even got a job without ANY formal modeling/texturing or anything game related, training/education! I can definitely see immense improvement from the start of the sketchbook towards the middle/end. I am happy to see you started a humanoid body, as they can be very intimidating to starters and many just avoid characters as a whole "until they are better", but to be honest, just diving head first into it all is the way to go. It forces you to get better, and I am very glad to see you did just that! Dont be intimidated! We are all here to help one another and to walk each other through each of our own weaknesses! Welcome btw! As for a critique, the main thing I am seeing is: You use a lot of triangles in your meshes. This is a bad habit that should be avoided when absolutely possible, getting into the habit of using tris can be hard to break (I was one of them, so you are definitely not alone!). The reason modelers try to stick to quads is due to the fact of making UV mapping as easy as possible for yourself or your in-house mapper/texture artist, it also just looks cleaner and is easier to read and easier to modify down the line. if you use quads, the "loops" these quads belong to become clean and complete, and these loops can be selected as a whole with a single double click to allow easy modification to the mesh. Another thing is; Dont be afraid to use multiple pieces to create your models, it is best to create single meshes when possible and when the item is a sing;e "object", but using multiple pieces to create your model can help with keeping the tri/poly count lower for games and for low resource situations.
Great job though getting started, I like your ability and confidence to dive into the harder more organic models as a beginner, when I started I tried to avoid them as much as possible, afraid of failure. Keep it up!