You have a pretty good list already. There are definitely still electronic component kits out there that are a handful of resistors, capacitors, and transistors of different values and some LEDs. You can also look at the parts in these kits and order them yourself from a place like Digi-key or Mouser, not sure what is available to you. It might save you a couple of bucks.
You probably don't need a variable power supply, unless you really want one. But you should be fine with a 2 or 3 AA battery holder that has some wire leads you can plug into the breadboard. 10k Ohm potentiometers are the most common and the only kind I think I used in school. You can also look into logic gates (NOT, AND, OR, NAND, XOR) to start getting into the digital side of electronics without a microcontroller. Logic gates are the building blocks behind modern computers. There are IC chips that fit into breadboards in the 74HC Series.