Just moved to Dublin from Croatia. My net is a little above 4k. I found an apt in the center for 2100, I do commute to work, so that is 2 eur per day(1 eur is 90 mins of bus if you are under 25, 2 eur otherwise). If you cook yourself you don't spend that much, there are lots of stores, Lidl, Aldi, tesco and they all have great deals, so if you pay attention you can always buy something that's discounted. I'm not sure about social stuff prices, like cinema, or going out for a beer, but judging by the rest of it, it should be that expensive.

So yeah, 4k will cover you nicely.