For general tinkering with basic principles, you could also keep your eyes open for kits (for example, I have an old 100-in-1 exploring electronics kit that hel

For general tinkering with basic principles, you could also keep your eyes open for kits (for example, I have an old 100-in-1 exploring electronics kit that helped me out and to which I intend to return one of these days as it had some good things for getting some familiarity with the basics). Such kits are often designed with educational purposes in mind, and as such include explanations of why the circuits work in addition to instructions for how to put them together.