Where to start with Linux?

I've wanted to go over to Linux for a long time but I have no idea how to go about it. I hear about incompatibility problems with hardware and all the different options for different Linux OS's and that's it, I forget about it for a while to avoid the headache.

So where do I start? I don't even know how to choose hardware or what to look for. The number of options with Linux makes things a little confusing.

And although others here have answered the question before, I'm unsure what I have to do to stay 'safe' on Linux. Are there extra steps or is it just the standard, don't open dodgy links and turn off Java script in the PDF viewer kind of thing? Does Linux come with a trustworthy firewall/antivirus/malware detection? Is there a chance of Linux e.g. sending my passwords, etc, to someone or just letting someone into my harddrive? I hear that 'open source' means people can check the code but how do I know if someone has checked the code—I wouldn't know what to look for myself.

I followed the Linux subreddit but the users the can be rather… enthusiastic, which is great, but I need something far more basic to get started lol.

Is there a good step-by-step guide somewhere? Or can anyone give me some pointers/tips/advice?

I mainly browse, type, and read pdfs and other text files. No gaming, although I wouldn't be opposed to it. No need to be mobile; laptops are terrible for my back so I always use an external monitor, anyway, so I won't be using it 'on the go'.