Really depends on where your interests lay. Someone who is into power electronics is going to be different from embedded micros and amateur radio. But if you want a general useful stuff list:
Multimeter.
Small 1 or 2 amp power supply with multiple outputs. Or just batteries if you are trying to keep it cheap.
Soldering station with a fine tip.
Rosin solder, liquid flux, alcohol, small needle bottles, solder braid and a solder sucker.
Misc small tools like screwdrivers, pliers.
Couple kinds of tweezers.
Variacs, oscilloscopes, LCR meters, logic analyzers are all pretty handy for specific sorts of circuits. Really it depends on how far you are going and what you are interested in working on.