It’s easy… start with the easy ones, then go harder…
Just learn the basics.
I am in the process of making a course on this on https://www.secretlesson.com. I will show how to learn the basics, then how to hack your code. Also, it will build to each level of practical knowledge I have used in the field as a website/app programmer.
Also, I will also have them on youtube https://www.youtube.com/channel/UCOgV9t68M2hkYS9Hw6hV8Fg
It looks like you may already know these…
The client side Front-End Development basics:
HTML - 1st (HTML5 later)
Then you can learn the easy back end development server side language:
but then I would say Python and .NET (C# with Visual studio community edition is free) are very popular for high paying jobs because of XAMARIN. Xamarin allows you to make apps between Android, iOS, and Windows Apps all in one shot. Also, C# is use in a lot of programming jobs with hospitals.
The problem with this job market is that you really need a good online interactive resume that shows your skills otherwise your resume is glanced over quickly.
Glassdoor will give salary and interview advice. Most of my jobs have come from having a really good LinkedIn profile and connecting to lots of people. But my online resume has made 3 times as many people search for me which I display on linkedin.