For pub-wear there it invariably boils down to jeans, shirt, pub jacket (to keep you warm getting there but dispensable) and non-sports shoes. The latter due to the fashion police bouncers that one may encounter outside some pubs/clubs. To get a visual feel for it you can check out the out and about section of the Belfast telegraph website.
Ah, that's some good advice, thanks. It really didn't occur to me that sports shoes aren't much allowed in clubs.
Yup, headed to UL. I'm really not as nervous about fitting in as I seem -- I just would prefer avoiding having an "oh shit..." moment or something once I set a foot down. I'm absolutely excited to take in a new environment, explore the country, and meet a whole new group of friends.
On point, I think a pair of Vans probably fit the bill for me just fine. Thanks again, everyone, for your responses. If you happen to have any other advise for getting around in Ireland in general, definitely shoot me a message, I'd love to hear it.