A low poly chess set: This is one of the simplest designs that can teach you about blender.

1. Building Collections

2. Sharing object properties

3. Using same materials

4. Using multiple modifiers including boolean and subdivision surface

5. Modeling in high polygon count and then converting them to low polygon count

6. Difference between low polygon count vs low polygon style

Eventually leading up to this final render. Sure, the render isn't anything special but I had learned loads from this exercise.