I'm getting involved with a dissident political organization and I want to have a private computer. Something where the feds or hackers can't see my images, text files or anything. I'm not going to do anything illegal with it but there will be sensitive information regarding rallies, plans, internal workings, locations, ect. and I want to keep that anonymous and private.

What kind of computer do I buy? What do I use? Linux? Tor browser? Can I still use my wifi? Can I use my computer from home? What kind of email do I use? How do I instant message people? Any security flaws I should be aware of?

No I'm not a pedophile and no I'm not a terrorist, I'm just an extremely paranoid retard. If anyone can drop some basic information I can do my own research and take it from there. I just wanna know where to start

Any and all help is appreciated :3