Dublin is an interesting place with many things that can keep you occupied and not hungry. But when you are a back pack traveler like we are it definitely helps to stick with your budget so you do not find yourself starving and off your budget before the trip ends.
Traveling through Europe in general leaves you with great alternatives that are outside the norm in the states, we do have discount grocery stores but usually so overly processed and untrustworthy. I mean lets face it… Even McDonalds is better in europe. Given the integrity and standards the food is upheld to, it allows you to try out the discounted foods and even the store made things which are very delicious. Im not saying to lower your standards but realize that it isnt that bad compared to busting your budget. Also, single fruits are just as cheap.
We ate at Spar quite a bit, with wood wire pizza slices, fresh breads, and a solid deli section you could easily eat lunch for just a few bucks. You can find the same deals in Tesco but found it to be a less quality experience when we would go there. You can always grab a sausage roll for around 2Euro
Another suggestion would be to keep an eye on the window menus and sandwhich boards which are very popular throughout Dublin. These signs have amazing deals from Taco Tuesday to 3Euro deli items. It is very easy to grab the standard break fast at the hostel or hotel in the morning, grab a pint and some snack and carry on to a nice picnic in the park. Phoenix park is just a short bus ride from just about anywhere in town.
Another thing to think about is to pre-pack travel foods like YumButter.com which can be traveled with the almond butter is great with apples!