Hi Laura
Loads of tips on Dublin for you!
Tourist - Guinness Brewery, Trinity College, Hop on Hop off bus.
Shopping - Grafton Street and surround, Dundrum shopping centre, henry street. Check out Temple bar for some smaller shops and second hand goods
Food - on the cheap check out Cafe Bar Deli, The South William, Green19, Pizza Stop
Drinks - Good areas - Wexford/Camden Street, Grafton st, Southwilliam street. Looking for a good Guinness try Mulligans on Poolbeg street or The FerryMan on St John Rogerson's Quay
Local - Outside of the city check out Howth or Dun Laoirghe you can get to both by train (DART).
Need anymore help just ask, hope you have a great time.
See you're also going to Valencia, I've been there too hope you enjoy it.
Amy