I think it's better don't buy amber if you aren't an expert. You never can tell, you could be swindled! Instead there are many beautiful wood carvings, sculptures made of stone and the typical naive paintings to buy.
What to buy: I bought a picture and this wood carving which is a Taino idol. Tainos were the ancient inhabitants of Hispaniola, then arrived the 'conquistadores'....
Shopping in the Dominican can be exciting or expensive...you must choose which...Please read my Tourist Trap Tip for more information.