Since you posted in Central I assume you're looking in Santiago, if so, here are my recommendations:
1) Super Rico - on John Pablo Duarte, near "downtown" - excellent, authentic, and reasonable
2) Pez Dorado - on Calle del Sol near the monument - excellent, authentic, but a bit pricey
3) Expreso Jade - next to Hotel Casino Matum - very good and inexpensive
4) China Fast Food - on highway heading towards Santo Domingo, across the street from Banco Central - not great but very inexpensive.
For inexpensive places in general, there are dozens and dozens...depends what you're looking for.
Try this site as a starting point, and choose Santiago, there are over 40 restaurants listed, most with their complete menus:
www.menu.com.do