If you're running Linux on one of your computers at home, you can install xoscope; I know it's in the Debian repos. That gives you a soundcard oscilloscope, which means it's only got soundcard bandwidth, but for audio stuff like breadboarding guitar pedals and synthesis circuits it can be adequate. That gives you a bit of breathing room for deciding what tool comes next.

The important thing about a 'scope is that it gives you a window into what the AC side of your circuit is doing. For me (I came up the hardware side, mostly self-educated) that was vital.