In reply to BennyBoy:
If you have a tent then the campsite at Prades is excellent and cheap. Otherwise the best cheap options are the rifugios at Mussara at Siurana.
For low grade stuff a good place to go is Margalefs (it's in the RF guide). Bit of a drive from the other crags but it's a scenic road. Once you've warmed up with a day there you should be right on for easier stuff at La Mussara, of which there is plenty.