39a's from the quays in Dublin leave roughly every 15 minutes. Get one of them 39a's out to the center and then the free shuttle bus to the college from there.
Times for shuttle bus :
In the morning time, the 39a is very quiet coming out of Dublin
and stuffed going in, and busy in evenings going back into Dublin but wayy busier coming out of Dublin at that time. So it works out fine.
There's student weekly/monthly passes you can buy for the bus once you get your student travel card sorted during first week of college. Before you get you hands on one of them, it's about 2.45 or 2.70e tops from the quays to blanch center.
It's much easier to get to the college if your inside Dublin. Btw the best spot to jump on the 39a in town is Aston Quay, on the quays, immediately opposite O'Connell street. There's also the 39 but it adds about 20mins onto the journey so best avoided unless it's raining ;D
Taking the 39a takes about 39-43mins to get in/out of town. Add the shuttle bus time ontop of about 7mins and factor in a gap between the two and you've got about an hour's journey at the start and end of your day. If you've got a class at 9am means you'd have to leave town at atleast 7:50 to make it in on time in the morning. So two hours every day back and forth in total. If you can live with that town it is. Trains are quicker but less frequent. The shuttle bus does swing by the train station too so it's also a viable option.