Adding on to the Windows Defender bit: it’s also a very good antivirus, so you can pretty much just get away with that and an adblocker on your browser of choice. Been running Firefox with uBlock Origin and Windows Defender for years now at this point and have not had a single virus nor infection on my computer - and I used to use Norton and Avast before that.
That being said, if you’re the kind of person that goes onto hella sketchy sites a lot of the time, might be worth looking into a paid antivirus.