How to get started with REST

Hi, so since lockdown I decided to take up learning every part of automation as best i can. So far over the last 2 months I've covered:
Basic Python
Building more advanced Python programs
Netmiko
Napalm
Nornir
YAML and JSON
Now after feeling comfortable with all those technologies I've moved onto the Requests library in Python and have learnt the basics of that. I definitely feel comfortable with Python now and didn't picture myself being this at ease around it within the time of 2 months, but 7-8 hours a day doing it in quarantine will do that to you i guess.I'm now trying to put into play my knowledge of the requests library with things like REST API's but its just hit me....HOW? Apparently Cisco host something to use, is this correct and how do i get onto it? Is it just more documentation or is it devices hosted by them that i can actually interact and start to play with a REST-API to get hands on use?Another thing too, you start learning one thing and then they hit you with the old...... "You should've been learning this instead" line were I've spent the last week or so getting to grips with the requests library and they go and say on their site...."learn Postman instead"......WHICH ONE IS IT? Haha! It's getting a bit silly now. I know Postman is a request GUI pretty much so learning the request library may have some benefit there but at the sametime i'm thinking everytime i think i'm learning what they want, another pops up instead.
I thought i'd put this question on here as it would probably get a wider response from normal engineers who are either using this tools in the industry now or are studying them...which ones should i actually be learning here and dedicating my time to? Because as we all know, there are a thousand different technologies out there with automation and i think it's impossible to learn them ALL.

Thanks for the help guys