Cheap flights are available from Ryanair and other budget airlines, and the next most important thing you have to consider is how much you can afford to spend on accommodations. There are different options available and your comfort depends on how much you are willing to spend. Check to see whether breakfast is included in your hotel before booking, as this may be an additional expense that you need to plan for.
There are affordable restaurants and bars around the city, and again it is a good idea to plan ahead in order to ensure that you know roughly how much you can afford to spend on each of your requirements. The following infographic from WebVoucherCodes.co.uk is a useful guide that you can use as a starting point for your budget holiday.