When I just started out using Blender, I familiarized myself with the program by making tiny worlds. Small, stylized dioramas that are strangely good at teaching you a lot of different techniques. It is how I learned the basics of modeling, particle systems, materials, and lighting.
the first thing I ever made in Blender!
the second thing I ever made in Blender! (not a joke)
a toy version of a vacation home I stayed at with my family
the fourth thing I ever made in Blender! (ok we get the point now)
suprisingly not the fifth thing I ever made in Blender (I got distracted doing architecture first)