I also use the free built-in MS Defender in WIN 10, which is now among the top rated AV software. Was not always the case in the past. I'd also recommend installing separate on-demand scanning software for secondary checks. You also need to promptly keep your OS, browsers, and apps updated with latest security updates as AV software won't necessarily protect you against these vulnerabilities. A layered approach to security is always advisable.
I'd don't pay for AV software, as many of the top rated security apps have have had instances of serious vulnerabilities. This can be a problem, as AV software require elevated privileges to run on your system, which can allow a hacker exploiting a vulnerability to act as an admin, and potentially remote access, install malware, or keyloggers on your system.