well the best thing i can suggest you buy is a freedom ticket from dublin bus (check it out on ) as it includes your bus fare to and from the airport on the airlink, access to the hop-on-hop-off tour bus service for three days and you can go on all the other bus services around dublin (as long as they are on dublin bus). its a bargain at only 25euros as your saving about 40-50euros; depending on how much you use it - you can buy this at the airport or at the dublinbus office on o'connell street or even online before you go!! so its perfect if you want to escape the city to go visit the countryside or seaside - places like malahide and balbriggen are nice although i would check in advance how long the journeys are! as far as night life goes - temple bar is the place to go; my favourite was oliver st. john gogartys - it has the best pub in town for music and meeting people (i must have met about 30 people during my three day stay in september - it was awesome!!) although the price of a pint goes up during the night (but this is to be expected everywhere in dublin!) temple bar is about 15 minutes walk from your hostel; not too far if your sober, but could become difficult if you had a few drinks on you... thats why we stayed on temple bar... for the convience if nothing else - but don't despair because there are still some good pubs over your side of town like o'sheas who tend to attract an older crowd - but a fun time is still to be had!! ive been to killarney as well - not stayed in a hostel there - was with family, but its beautiful! best way to get there would be on a bus from the bus depot in dublin city centre, you can get to any part of ireland from there, otherwise the train is pretty good, but the train tends to be more expensive, but worth it if you want to get there quicker!!
if you need any other info or have any questions, ill do my best to help!! just drop me a line :)