The firewall that comes with Windows is a decent product. Although I can understand if someone wouldn't be too fond of the "workflow" imposed by its interface. On this forum alternative GUI's are mentioned for this firewall, that should make it easier to use (by 4wd, if memory serves). Make such a bundle work, combine it with Windows Defender and add a hint of common sense, that should keep you already pretty safe. Use an online virus and scanner and malware scanner on a regular schedule too for piece of mind.
Tuxman is quite right about AV software wasting more CPU cycles than they are worth.
I do all of the above, while being covered by OPNsense
router software, which comes with a good firewall too and allows for much more filtering of network traffic. It runs on a 9 year old dual core Athlon PC with 2GByte of RAM and 2 network cards, but it can run on much less powerful hardware if the amount of computers that make use of its functionalities is low). Besides the occasional donation and the consumed energy of the box it runs on, it is free and awesome!
Using it can be as easy or difficult as you want to make it. Meaning that the setup wizard makes things easy, but you can also go and tinker with its vast amount of settings yourself. It all depends on what you want to do with it. Yes, I'm a fanboy.
Nowadays I am much more worried about malware than computer viruses. Granted, I haven't visited the "bowels" of the internet for years, which helps reducing risk a lot too.