Before worrying about the antivirus, it is good to understand that the most important security tool is the observance of the basic rules of computer security: keep your system well updated, use the utmost distrust of any executable (especially if downloaded from not authoritative source) and, more in general, to think always twice before clicking.
That said, the antivirus is a second defense's essential level but, if you use Windows 10, WD and Smartscreen offer an adequate malware protection.
Eventually you can add Zemana Anti-Malware free or paid as a second opinion scanner.