hey, welcome aboard.
you've already taken the first, most important step.... working.
as long as you're putting pencil to paper or whichever medium, you're heading in the right direction.
check that image out... notice the highlight at the bottom of the sphere, that's your bounce light coming off of the surface the sphere is either on or above. dont shade the sphere all the way to the ground. also, notice the difference between its lightest point and its darkest... your red sphere is almost all one shade if you squint at it. add some contrast.
keep on trucking, m8.
use some reference for your drawing and just keep pumping them out.
ambition makes you look pretty ugly