Best way to get to Galway same day arrive on international flight in Dublin

Flying into Dublin (best option for our international flight) on Dec 20 and wanting to go to Galway the same day. Irish Rail doesn’t have a timetable up past Dec 7 but I assume there will be a train option. Two questions:

1. Does it make more sense to just fly since we’ll already be at the airport, head to the train station and go from there, or is there an option like a bus from the airport to consider?

2. Depending on the response to #1, how much time should we allocate between landing at DUB (from the US) and getting on the next mode of transportation?

Thanks for any guidance!