Most WV state campgrounds are very nice. We enjoy Sherwood Lake. The campsites are well-separated and private. We've also been to Watoga, Pipestem, and Babcock, which we enjoyed.
I went to Killens Pond in DE last week. Thought it was very nice and wasn't expensive at all. I had a primitive site no electricity/water and managed pretty well. Caught fish out of the pond to eat although some fishing areas were difficult to access. Across the pond is the main part of the park. It is near Felton DE south of Dover but just north of Harrington. Overall I rate it 4/5. On the campers side you don't have to pay the daily park entry fee. If you go during the week plan on bringing items because the camp store is only open on weekends.
Thumbs up on that one. Stayed there a few years back in one of the log cabins. Kids had a blast reading the cabin log, stories other folks wrote when the stayed there. Rental kayaks down on the river, a pool also.
Oh, and if you have access to military bases, Fort AP Hill has camping also, and great rental cabins right on a pond.