It is highly recommended that every computer user have a good anti virus software installed and also, only download software from known sources to minimize the risk of ever installing a bad or virus infected softwares.
I'd only recommend a antivirus if you have no clue about computers, and don't know how to stay safe using them. Even then, I'd consider the very software which calls itself antivirus, a virus itself. They usually come bundled with a ton of stuff that you don't want, or they hog up your computer resources for no benefit to the end user. You can effectively safeguard your computer from most attacks, if you are careful, and use it with security in mind. Seriously, Anti Viruses suck. They also give a false sense of security, because as soon as a user installs them, they assume they are safe. Any malicious user, that is at least competent, i.e the ones that are actually a threat know how to avoid detection from anti viruses, simply because they are effectively reading from a database of known code or patterns which indicate a virus. Plus, you get a ton of false positives, which can be problematic in itself.
If you verify each download that you download, assure the signature is correct, and then you safe guard yourself against some of the common attacks on the internet, such as script attacks then you'll likely be fine in the most part. The more advanced precaution you could take is either physical isolation or virtual compartmentalizing with an operating system like QubesOS. I've talked about this in the past, so I won't go into detail about it here, but most users can safe guard themselves without actually needing a anti virus.
