Well, it depends what you're interested in. There's the handful of outlets that will serve you Irish craft beer; and then there's the classic Dublin pubs, virtually none of which will serve you anything except factory-made blandness.
As a beer lover rather than a pub lover, you'll presumably be wanting the former, so that's Messrs Maguire (Burgh Quay); The Porterhouse (Parliament Street, Nassau Street and Cross Guns Bridge) and The Bull & Castle (Christchurch).
And welcome to the group.