As I said, depends what you want.  There are B&Q type places in Tarragona (Reus and Tarragona are virtually the sale place.)
There's a Bauhaus, Leroy Merlin and Carrefour all on one trade park just off the motorway in Tarragona (easy to get to, about a one hour drive).
There's a Bricorama at Vinaros (along with other stores such as Carrefour and electrical outlets.
Irrigation kit is available locally (Amposta for instance).  Tell us what you need and I'll give you directions.
Only local shops in Santa Barbara.
A good timber yard in Amposta.