My current recommendation when I get asked that question is not to bother with any third-party AV and just use Windows 10 with Windows Defender (unless they're on OS X anyway). When I'm asked to set things up, I switch their default browser to Chrome (or Firefox for those who "don't like Google"), add uBlock Origin and use Click-To-Play for plugins (which, surprisingly, isn't much of an inconvenience once you block ads anyway). If someone asks for extra protection, I add OpenDNS Umbrella to the setup ($20/year for 3 devices), which is a nice additional layer of defense. Chromebooks are also a great option if someone's not doing much other than email, web browsing and such.

My other recommendation is to use a tablet for things like online banking. (Yes, even an outdated Android tablet is probably less likely to catch malware that will steal your money than an average computer.)