I have found the easiest and safest way to secure my pc was, to change OS to linux and be careful what you download. Always scan possible shady links here
https://www.virustotal.com/en/ I also use Clamtk and Comodo just in case
Like Vervolioman said, linux does have fewer vulnerabilitys if you use it correct (for example, only install software from the original repo, stay away from privileged accounts,...). Even then, you should always use virustotal/avast when installing untrusted software...
If you stick to windows, i would defenately use a good AV, i would recommand McAffee, since it's pretty good and pretty light for your HW recources.
If you download untrusted software (like a new altcoin wallet), scan it with virustotal AND run it in a sandbox (i recommand the free version of sandboxie).
Also, wether you use linux or windows, make sure you update your OS regularly and run a decent firewall...
