One way is to join the Free Software Foundation as an associate member:
https://www.fsf.org/associate/
Not only would you be contributing financially to people doing great work,
but it often leads people towards IRC and XMPP chats with people who might
have some ideas for you. But the easiest way to contribute is to spread the
word to friends & family, and boost good blog articles on your social media
accounts.
Before committing yourself to buying fully-free kit, you should spend some
time using Trisquel GNU/Linux on your existing devices. You will find things
you are no longer able to do, and can make a judgement call about whether
this is the right route for you. Once you've spent a few months with the
system and want to take the next step, take a look at this list of suppliers:
https://libreboot.org/suppliers.html
As for getting a job with the FSF itself... that's quite tricky as they don't
come up very often. If you want to switch career tracks try learning Java
(not JavaScript) as you'll have a wide pool of software houses and
consultancies to choose from.
While I would love to work exclusively on free software, you'll probably find
like I did that's not always possible when you want to put food on the table!
The team I work in is called the "Open Source Software Engineers" not because
the code we write is free software but because we used open source languages
and technology stacks to write proprietary middleware systems for clients. I
also have to run Windows on my work laptop because the corporate IT policy
mandates I must. (This is part of the reason I'm now retraining as a
sysadmin)
