Get a leapcard which you can use on the bus, train (Dart) and tram (Luas). You tap on to a bus, but you tap on an off the train and tram as card points. With a leapcard you can top-up using the mobile app, at shops or at train and tram stops.
In Dublin, the electric rail system called the DART (Dublin Area Rapid Transit) is a quick and easy way to get around Dublin. It runs along the coast of the Irish Sea from Malahide or Howth in north County Dublin southwards as far as Greystones, Co Wicklow.