antivirus is bloatware and will slow your system down.
however there is nothing as important as peace of mind so my recommendation if you are new to android and feel an AV will rest your mind go for an app that also provides other services. lookout for instance is an AV *and* it has anti-theft tools, if that is your thing. clean master is an AV and cleans leftover cache or junk stored in your phone over time...
myself particularly avoid AVs like the plague. i ditched clean master once it included an AV engine in favour of another that does just maintenance. but that's just me and everyone uses their phone differently. if you download torrents, visit dodgy sites and download pirated apps perhaps you need one. i know i dont.