If you are not to backpack, bringing a good load of clothes shouldn't be much of a problem. Do you know what is your airline luggage weigh limit? It is usually around 50lbs.
My way to have some variety on the road is to bring shirts, pants and skirts that all match. So it kind of doubles the selection.
What will you not use ? It depends on your lifestyle in Ireland. Will you go out a lot, work, study, do outdoors/indoors activities... ?
people are people