I bought a tutorial course on Udemy a while ago, did just a handful of videos and came back to find a surprise! They're updating their course to Blender 2.8, which is great! So I started watching it from the beginning again.
The first chapter 'challenge' was to do a few models trying to use only primitive shapes, keeping it simple and model from life or some other reference, so I went and modeled a couple of houses I've seen on Artstation.
This is the reference for the first model I've made; https://www.artstation.com/artwork/yKzOJ , which I kept to mostly basic shapes and modeled mostly by duplicating blocks.
This is the ref for the second; https://www.artstation.com/artwork/WgZKN , where I used a whole lot more custom shapes, merging objects and vertices, also tried to fiddle with sculpting to make the terrain on the left and some ico spheres for the rocks!
It took me about 5 hours to do each, and I'm very happy with the results, since this is my first real work on Blender!