Vue.js, it's the simplest of the popular frontend frameworks

You can learn a hellton about sysadmin and DevOps by running a home lab and aiding that with some courses and maybe one cert or two but I wouldn't splurge on certs that readily.

Golang, Express.js, Nest, Flask, SQL (a must), maybe Spark if you dare. Any popular and expressive framework/language for full stack/backend, except for Rails and PHP, those are dying technologies despite their still relatively high popularity in some countries.

Maybe Flutter, Swift or React Native if you want to get into mobile dev.

Just go to a job board, then to learnxinyminutes.com, pick something and start with building small, then medium sized, then maybe more complex projects or contributing to FLOSS written using your tech of interest (but please, PLEASE don''t treat OSS contributions primarily as a way to get a job. Pick something you use instead. Try to figure out how you would implement something, do that and don't let the impostor syndrome win if it uses a tech you're familiar with whenever you want to open an issue on a git forge.