Welcome to the community. While I think this topic is debatable in the sense that it is all preferential; No one developer does things the same (for the most part).
**Edit: This is not a comprehensive guide. It is merely a starting point.
I use Local, VS Code, PrePros (windows pre-processor), Firefox (dev edition), Chrome, and the shell for git mostly. (Always test in multiple browsers)
Start on YouTube and Team Treehouse. There are also some bigger names like Zac Gordon (paid) that have good courses in starting a foundation in WordPress. With that said, I recommend getting up to speed with HTML, CSS/SASS, Javascript, and PHP to start. You should start simple and use HTML and CSS to get a foundation in them before branching to libraries and other languages.
Once you’ve gotten things setup I recommend always using the “Inspect Element” option in the right click menu when in Chrome or Firefox. The dev tools section is powerful and can uncover things if something doesn’t work the way you expect it to.
I also recommend looking into git (version control) - that is after you have a foundation in the basics of shell / terminal commands as well as the above.
It will only add complexity when you are first starting, but is essential.
Google and StackOverflow are (sometimes*) good sources of information.
Don’t be afraid to break things and always keep backups. (this is also where version control comes into play if you can’t fix said broken thing - or don’t know what you changed - git will tell you everything that has been done (code-wise) and is also conveniently integrated with VS Code - some setup required).
The Codex has good info for starting with a Child Theme - which will get you off the ground with a somewhat custom theme you can build and all of the niceties set up for you. After that would be custom theme development where you build basically everything and make it easily editable on the backend for the client (or yourself).
The track “tracks/beginning-php” on Treehouse starts with the basics of HTML and works up to a soft introduction to PHP. There are a lot of tracks and you have to be somewhat of an autodidact or just enjoy it (like most of us).
While working in WordPress, the Codex will be your best friend. Learn to read it and utilize it. It will also help you start with WordPress before digging deeper (link below).
Child Theme Codex (requires basic understanding of PHP to start)
https://developer.wordpress.org/themes/advanced-topics/child-themes/
Good luck and stay diligent!