- Digilent Analog Discovery 2: Low-end 30MHz oscilloscope+function generator+logic analyzer controlled via USB. $279 (or $179 with student discount) I think of it as 'swiss army knife' of electronics: it's not as good as a real oscilloscope, function generator, or logic analyzer, but it does the basics of all those roles and fits in your pocket. http://store.digilentinc.com/analog-discovery-2-100msps-usb-...
- Xprotolab Plain: Same general idea as the Analog Discovery, but only $20 and therefore an order of magnitude crappier. Only 20kHz bandwidth. Suitable for an absolute beginner on a tight budget. http://www.gabotronics.com/oscilloscopes/xprotolab-plain.htm
- Extech EX330 multimeter: It's a multimeter, the most basic instrument you'll need. $53 on Amazon. I recommend getting some alligator clip probes; I find them much more useful than the pointy probes it comes with. https://www.amazon.com/gp/product/B000EX0AE4