Welcome to the Forum!!
Gettysburg is among our favorite places to go. Lots to see & do. Our CG of choice is Gettysburg Campground (not to be confused with Gettysburg Battlefield Resort CG). Drummer Boy lost our business years ago when the corporate crowd took over; Granite Hill was just plain hostile to us, for reasons I'll never understand.
We have visited the other CG's in the area - Round Top, Artillery Ridge and the KOA. The KOA is very nice, but we thought the sites to be small. Was not impressed with the other two.
Since you're coming from Dayton it is tempting to think I-70 to Rt. 30 to Gettysburg as it appears to be the most direct. IMHO Rt. 30 is slower and has some grades/curves that are not too pleasant. See the thread referenced by brirene. Even though the Rocky Mountains are higher and steeper, the Appalachians are impressive in their own right and often surprise folks driving through the first time.
Enjoy & safe travels.