There are a ton of different directions that you can head in and focus on. I encourage you to start/look at stuff that you're genuinely interested in and excited about.
Awesome! Great to hear. Feel free to ping me if you have questions.
depends what kind of security researcher. AppSec is p hot rn. Mobile sec is p hot. Browser security research can still advance quite a ways. ExploitDev is always popular. Just depends what niche you want to go into. Once you know your niche, just start publishing research (vulns, analysis, something interesting FFS) and sharing it online. If the research is legit, it's not hard to get noticed.
I especially like the last sentence here. Thanks
Contribute to open source security projects/tools.
It wouldn't hurt to go to Security conventions and start networking.