If I were in your shoes (and I often am, in various other contexts), I'd get the cheapest SDR dongle, and then use your favorite search engine for tutorials (there's plenty).

First two hits for "how to get started with sdr" on duckduckgo give you awesome starting points: - https://www.rtl-sdr.com/rtl-sdr-quick-start-guide/ - https://hackaday.com/2012/06/27/getting-started-with-softwar...

From there, figure out what device you're going to target. The 434 MHz devices are quite ubiquitous (and easy to understand) -- door bells, old school thermometers, remote switches, what have you.

Even without your own device, I'm sure you will find plenty of traffic near you (if you live in a reasonably densely populated area), so you can at least practice.

And then it's down to grinding it out -- read docs, experiment, repeat. :-)

HTH.