I'm gonna bite...
Spectrum/Network Analyzer: HP 89441 or 4195A alternatively a Signalhound : Although those would probably already eat half the budget. Or maybe the whole budget if you could get a more modern late 90ies or early 2000s model.
Signal Generator: again something from Signalhound. Seems affordable for what it does at first glance. Benchtop options doing similar stuff are gonna be four times the price and more looking at Keysight/ R&S.
LeoBodnar GPDSO and a distribution amplifier. Used Stanford Research ones are currently available on ebay. Just convenient to establish an accurate frequency source for all the instruments you could ever have.
Picoscope 5000 series like the 5443D USB oscilloscope. Capture EVERYTHING till 100MHz and below.
An used SMU Keithley 2400 or similar or even a Curve Tracer when you can find one. HP4155 and up.
A reasonable high power DC Supply. Like a TTI CPX. I got one and having a relyable easy to use supply is just a godsend. R&S or Gossen Konstanter ones are nice too.
A Selective Level Meter. W&G SPM-16. Around 500 and the best and heaviest (analog) radio you can ever have if you want to misuse it for that. I would do it just to do it.
50

controlable attenuator. Just convenient to get Signal Levels to where you need them on instruments. R&S DPSP or similar. Some higher power fixed ones too. Like 3dB 5 Watts or so.
BNC or N connector peripherals in general. Some DC Blocks, Shorts, even Dust caps (expensive for what they are) maybe even a quite complete 50Ohm mechanical Cal Kit combined with getting it characterized if possible.
Tbh for me the (older) Instruments themselves are as much as a hobby as doing projects with them. So take this selection with a grain of salt. Although I would seriously consider getting "Peripherals". All the stuff you might need to make the instrumetns themself useable to you immediately after buying it. Like a set of 500MHz probes for example. Having the Instruments is one thing but having the cabling to immediately play with them after arrival is another. So some standard stuff would be money well spent the rest you can put in the bank to get a good ebay opportunity.
EDIT: teh SDS2104 can only go to 350MHz upgraded afaik. The 2304 can be upgraded to 500MHz iirc.