Wanna have fun? Go on with digital electronics: logic gates (AND, OR, NOT ect), switches, diodes, leds, resistors... maybe even registers (PIPO, PISO, SIPO, SISO). And then try adding capacitors (look for schematics online) to make the leds "breathe" (slowly fading in and out light). They're a good way to approach electronics form the newbie side.
Starting with transistors, amplifiers and oscillators at first it's not really a good idea, you'd better have some basics first
As for some real analog electronics I'd suggest giving a look at filters, but this may require some knowledge about signals and how filters "filter" them. But it's pretty much an easy job diggin with some random RC filters, so go on!
oh, almost forgot... if you really think you're able to get it about crystal oscillators.. here you are:
https://www.electronics-tutorials.ws/oscillator/crystal.html
Seeyah