You are getting really good advice here, and I agree with all of the above.
Your first sketch wasn't bad at all, it needed a bit more contrast, looseness in shading strokes, a softer drop shadow and overall a more expressive feel.
What I mainly see is that you are trying to get those ellipses too perfect while as you can see in yo's sketch, even if the ellipses aren't perfectly drawn, the overall sketch gets a much better character if you let your hand flow with the lines. Work from the shoulder, it will help you get better ellipses. You can also see how fluid strokes on the outlines that continue past the perimeter of the sketch, and some overall effect and perspective help a sketch come alive.