Put your drawing on top of your reference in your favorite software to spot the small errors that can totally destroy likeness. Do this not until you have done your very best to find this through construction and measuring, and a good night of sleep. Try to find out what went wrong, and how you can avoid your own personal pitfalls next time.

This is exactly like the choice of lenses in photography. You are free to pick a lens with wide angle and short focal distance, which offers you a broad view which emphasises perspective, or a lens with narrow angle and long focal distance, which brings things closer to you, at the cost of flattening things out.

Looking good! The door is a little wide, though.

I like it! I suggest you emphasize the main act of this composition, i.e. the robot-like character studying the doll head, by making everything else support this act, subduing whatever conflicts. For instance, Pinocchio's head in the top left is really nice, but it draws away my attention from the main act.

Check your proportions: the pelvis block should be a lot bigger. It refers to a big element which carries a good deal of your body weight!

You may want to start with a quick gesture, to layout what goes where, and then place your blocks? It helps to separate planning from execution.

There is nothing wrong with textures: respect your materials! I think it is funny how some try to get rid of textures in natural media, while digital artists do their best to get texture, simulating natural media.

I reshuffled the values a bit, to get rid of accidental deep shadows, like under her right arm, and make her fit the 5 value palette a little better. Feel free to shoot!

I support Sonja Müller's suggestion to do color studies. In addition, pick up some color theory. Some suggestions are http://www.huevaluechroma.com, http://handprint.com/HP/WCL/wcolor.html Definitely study Johannes Itten's seven colour contrasts.

A drawing is worthy of feedback if you do not know how to improve it yourself. Give it your best shot, give it a good night of sleep, fix the problems you can, and then ask somebody else for feedback.

Looking good, in addition to using more of a value range, I suggest you vary your lines for a more interesting piece, for instance using soft lines for soft hair.

Good work! Please be aware that the rib cage fits a 2x2x1 box, while the pelvis fits a 1.5x2x1 box (check out https://www.youtube.com/watch?v=uJMoplyGboI). Your pelvis is not high enough, by far!

The web already is a huge sketchdump, who needs more?

I kind of struggle with this too. I can be very hard on myself. Something that helps me when I get frustrated is looking at my old drawings to see how much progress I've made. Either that or taking a break and doing something that takes my mind off drawing even just for a little while. Hope this helps!

There is a lot to like about this, but you could have been more adventurous in choosing your colours. Try to add some cool colours?

How about doing some studies of simple objects, like spheres and cylinders, in a shadow box, i.e. a box painted black on the inside to rule out accidental reflections, with a single light source? Post the results here!

I suggest you integrate perspective into your studies.

I think that, apart from the single character, the composition is too uniform, and not very interesting. Your character is just hanging there, looking, but there is nothing to see?

I suggest you spend more time analysing the relation between pelvis and ribcage: is it a twist or a bend? When drawing these as beans, exaggerate this relation!

I suggest you study Proko's videos on shading, which teach a solid understanding of light and shadow, instead of just copying photos. He exaggerates the core shadow, and you may or may not like it, but it is a good example of a somewhat stylized approach, with a solid foundation.