You might also find this piece helpful:
Excuse me, do you have a moment to talk about version control?
Jennifer Bryan
It's an expanded version of the "Why Git? Why GitHub?" intro of http://happygitwithr.com.
http://happygitwithr.com is mostly about installation and early workflows. The article above is a general explainer and motivator. There is some pain involved in starting to use Git, so it's important to know why you're putting yourself through this.
I would never advocate adopting Git w/o also using GitHub or GitLab. The remote, web-by, potentially collaborative aspect is a huge part of the value proposition. Being able to click around your files, at various commits, is incredibly helpful and no local Git workflow approximates that very well IMO.
I'm also a big believer in a graphical Git client. I use SourceTree but I think GitKraken also looks very good. It didn't exist when I started this journey and I don't feel like switching. I also use RStudio a lot for basic stuff. Anecdotally, I think new Git users tend to make more mistakes when they only use command line Git. It's just harder to see the state of the world. I think graphical clients are really useful when you're still trying to digest the concepts of Git.