One thing I wish more beginners learned early is to get the circuit working before worrying about making the project look finished.
It's tempting to assemble everything, glue the components into a case, and clean up the wiring afterward. But when something stops working, troubleshooting becomes much harder if you can't easily reach the connections or remove a component without damaging the build.
I'd much rather have an ugly prototype held together with tape or a temporary enclosure that works reliably than a beautiful project that fails because one wire came loose. Once the electronics are tested and the code behaves as expected, then it's worth spending time on the enclosure, cable management, and finishing touches.
I also think simple first projects deserve more credit. Helping a child build something that lights up or responds to a button can teach more practical skills than immediately attempting a complicated macro pad with a dozen features.
Get it working first, make it reliable second, and make it pretty last. That approach saves time, money, and a lot of frustration with DIY electronics.