When you plan your trip, it's good to plan how will you go from Dublin Airport to your accommodation (hostel, motel, B&B, etc.).
Why? Well, you don't want to be stupid and behave as if in a 20th century. If you can buy transport tickets online you can not only save the money but also avoid spending your cash on a street.
Good place to look to (if you are living outside The City (read Dublin) is getthere.ie or national.buseireann.ie web pages. I prefer getthere.ie since it gives you all kinds of transportation between cities (bus, train and very importantly lift sharing where you can offer someone a ride or ask someone for a car ride to your destination). Some prices will be visible immediately, but for some you have to visit bus or train web pages where you can buy a ticket.
To illustrate this a bit. I needed a bus from Dublin Airport to Athlone bus station. Regular cost is 14 €, but with online booking it's 13,30 €. If you become member of Buseireann, you get extra points for each online purchase. If you spend 10 € you get 100 points and if you have 1000 points you can change it for a 10€ ride. So if you travel often to Dublin, every 10th fare is free. When I've joined, there was another surprise - 5€ discount on first travel. So, instead of 14 € in bus, I printed my ticket at home (you can send it to your smartphone as well) and saved 5,7 €. Try to imagine this in Croatia.
If you are staying in Dublin area, I recommend buying Leap card with which you can use almost all Dublin transport system (bus, tram, city rail - DART) and on average is 20% or more cheaper than buying your ticket on the spot. Also, you can use it in Cork, Limerick, Galway and Waterford.
It has something called capping which is ingenious thing. You can use any combination of Dublin Bus/ Luas/ DART/ Commuter Rail per day for a fix cost of 10€. Knowing that adult ticket for a 4+ stations outside inner Dublin center is about 2,5 €, 1 zone by Luas is 1,8 € and DART 1st distance category is 2,1€ and one plans to visit many possible employers in a day, this card can save you a lot of money (see: www.leapcard.ie).
There is also visitor card 10€ per day, 20€ for 3 days and 40€ for a week (Monday to Sunday).
Best thing is you can buy your leap card at the airport T1 (Terminal 1, planes from Croatia) help desk (near exit/entrance to the terminal and close to Dublin Airport Taxis and Bus station (Red 10).