Learning electronics is awesome. I recommend the book Art of Electronics and the accompanying Student Manual. Back when I was a kid, you had to spend a small fortune to get electonics parts (with minimum orders of $200). Those days are gone. You can use Digikey and Sparkfun to get all sorts of cool gizmos on the cheap! But if you don't want to spend money on parts, you can use LTspice, which is a great simulator and learning tool (we actually design all of our circuits in LTspice).