You can make your own project, with arduino and a bunch of components. There should be a project that will require use of different techniques, like using a transistor instead of a relay, using resistors to not burn up components, using a voltage divider circuit (requires 2 resistors), and other techniques.

I am a beginner, so it would be hard to suggest what project to implement. I mainly used resistors to not burn the arduino I/O pins, and voltage divider circuit to step down the voltage for components with voltage different than 5v.