As long as you keep to the usual, reputable sources of apps (Play Store, Galaxy Apps, Amazon...), then you should be OK and no AV should be needed (Play Protect should be plenty enough). BUT if you're in the habit of visiting shady sites and side-loading a bunch of apps, then yeah, maybe using an AV might help a bit.
What you could, unfortunately, still find even in the Play Store, are apps that might push annoying ads to your lockscreen or notification bar. No AV would have stopped them, but at least an Ad-Network detector might be able to, well, detect them so you know which one to uninstall.