Aspiring freelance/junior web dev here, I'm familiar with WSGI (using Flask), some PHP, Apache, JSON, and Vanilla JS. What other technologies should I be learning to make myself more marketable?

Laravel, node, buncha js fws, jsp

I'm learning Jinja with flask, and am familiar enough with SQL to use it

Photoshop and Illustrator I've been using for years, I'm also a photographer which helps

Official education or open source contribution. With no education you have to show off earlier projects.

@norman70688 follow up: Java,C, C++, C#, Golang, brainfuck, whitespace, assembly, Einsteins equations of relativity, rocket science, religious rituals of Buddhism...

No but seriously, get used to git and version control early on. You said you know vanilla Javascript. Take a look at node, a Javascript engine for the desktop. It basically gives you access to OS specific stuff like filesystems etc. Use some popular front end frameworks. I would suggest react. It is used by a lot of large companies and the "goto" library nowadays. Makes sense to learn those first before smaller libraries like vue. Golang should be something that you should really consider to learn. There aren't a lot of golang programmers out there and it is a real alternative ad backend language instead of js and node.

Right now I'm working on full stack. I'm decent with CSS (without frameworks, but I'll look at the ones mentioned), and have been working on WSGI as a way to expand on my back-end skills, because I find it easier to use and modify compared to PHP. Version control is something I've been using for a while, both with a gui and command line. I appreciate all the tips guys !