I don't know about others but what I believe is that an antivirus makes our system slower because it keeps scanning for viruses frequently.
Also, downloading antivirus from unofficial sources would likely get you more viruses in your system.
If you still want to install an antivirus I would recommend you Malwarebytes because it is light and efficient and gets the job done.
Adblock and ublock are to block ads on a page. I have installed ublock and ghostery and use Duckduckgo to improve privacy and stay on safer side.