Avoiding viruses is so easy.
1. Browse smart. Don't go to porn sites, pirated movie sites, public torrent trackers, open suspicious emails etc
2. Add-ons. If you're using a decent browser you can find add-ons for it like an ad blocker, or something like NoScript for Firefox that prevents all JavaScript from running automatically on a page.
3. Should you find yourself with a virus after these precautions, these days it's fairly easy to restore your PC while still keeping all your data.
I've run no antivirus for like 10 years now, only had to restore my computer once and that was because I took a risk trying to find a cracked version of Photoshop. These antivirus programs all too often are resource hogs that just love to remind you that they're out of date and need to be paid for.