As a generalization: Enterprise languages. Java and .NET are probably the most prevalent across general-purpose software developer jobs these days. A lot of the “new-stack” bleeding edge startups are looking for node.js developers and a variety of front ender experences like Angular, React, etc.
C# and Java are quite similar.
C++ dominates the embedded/tailored jobs but you really need a lot of industry-specific experience in order to be considered for those positions.
If you are market language focused I’d look at your favourite local job site, drill down to all the programmer jobs, and then do a quick tally of the languages required for those. You’ll quickly gain a pretty good understanding of the majority of your local market.
If you are young and lookng to study, go to uni and do a computer science degree. That is the basis of all your programmy knowledge. Alternatively, you’ll need to get passionate and start bashing on some stuff to learn the language and all the auxilliary shit around it. SQL for data storage, configuation file languages, good design practices, etc.
Software is an art form and it’s friggin’ hard, when I interview developers I am not looking for people who just do it for money and have no base: You either do it because you’ve chosen it as a career and have studied it, or you’re a passionate person who has done a bunch of mad stuff just cause you like it.
Most programmers who have a computer science background go into grunt jobs just sit down and bash out work items all day, which is fine, but you need to study.
When I am interviewing I couldn’t care less about the traditional "tell me about a time where you worked in a team" pre-meditated bullshit questions where someone can formulate an answer in front of a mirror, I ask people about rad projects, what they like to develop, open-source they have contributed, and whether they can effectively communicate with a bubble in their voice and a fire in their belly about what they are doing with themselves. Bonus points if they bring in a laptop and we can sit and go over some code.
Employees who can communicate with a bit of passion about software are more valuable than people who can rehearse a standard interview. Means you’re more likely to communiate and not be a giant arse to users or stakeholders, and more likely to think for yourself. Above all, you’re more likely to do a good job if you actually care about what you are doing.