In the restored area everything is expensive. Your best bet for dinner is any of the plethora of restaurants along US 60 (Richmond Highway). There you have the normal chains (Cracker Barrel, Applebees, etc.) as well as a few Mom & Pop's. One we've always enjoyed is The Jefferson. It's not as cheap as the chains, but it has a nice ambiance. Any, they have good peanut soup (a must when visiting VA). Also I can't remember if they have Sally Lunn bread or not (another VA delicacy) The taverns in the restored area are very good, but expensive.
One bargain tip is to visit the pottery in Lightfoot (along US 60). They make all the pottery and things for CW and they are open to the public. You can buy the same stuff for about half the price or less if you don't mind buying "seconds".
For OBX, I can't really help you too much as we always rented a house. You will find OBX is pretty residential. Also, as with a lot of beach towns, most of the restaurants are Mom & Pop's. Are you staying in a house? There is a Wal*Mart just before you get on the island, if you need any "beach stuff" or other staples.
There are many cheap things to do in OBX besides the beach. One is to visit the Wright Brother's Memorial. Another is to visit the sand dunes of Kill Devil's Hill (bring a kite). There are a couple of light houses that are open to the public, Currituck and Hatteras. Lastly, if you have the time, drive to the tip of the island of the island and take the ferry over to Ocracoke. I think the ferry is free and Ocracoke is a quaint little town.