Think comfort and it depends on how you like to dress. I ended up wearing Jeans most of the time, and capris when the weather was a little nicer. I did bring a black knit skirt that I could wear with a couple of different dressy shirts. It is very casual, there is one dinner at the end of the week that is dress up, but nothing fancy. For shoes I had Merrell barefoot tenna shoes, which were extremely comfortable, but I think any good tenna shoe would work. I also had a very comfortable pair of black crochet TOMS, also great to walk in. A pair of Teva sandals, that I wore in London(we visited London the week before and then flew to Dublin from there), but didn't wear them in Ireland.
Pack a backpack or some kind of bag to carry stuff in for the bus. I had a small daypack that I used for walking around - camera, very sm med kit(bandaids, motrin etc) and anything that you would want while you walk around. But you can also carry a separate bag for the bus, you can keep extra stuff in it like rain coats, umbrella's, things to do on the bus(books, cards etc) this bag can be left on the bus while walking around.
Denise