[G0HZU_JMR]

In my student days I started out with a low cost multimeter and I made an RF detector probe and a crude signal injector.

The RF probe was the classic diode detector type that converted RF to a DC voltage that could be measured with the multimeter. It is possible to faultfind and repair radios quite successfully with just these low cost items. However, it wasn't long before I bought a scope, an RF sig gen and a frequency counter.
In those days there was huge demand for CB/amateur radio servicing so I was repairing quite a few radios a week using this equipment. Those days are long gone for me now, I think I stopped doing that stuff about 30 years ago.

I'd also include a capacitor tester if you want to work on vintage gear and also some form of ESR meter. You could probably buy all of the above today for a few hundred pounds if you buy older test gear although I would recommend to try and experiment with modern technology as this is going to be more reliable and much more versatile.