I would add to the attic. US Dept of Energy has a website that suggests insulation levels for based on your zip code. West Virginia attic is R-49 (I think). Fiberglass batts or rolls are usually cheaper than rigid foam. Make sure you already have a vapor barrier and the new insulation is unfaced. I wouldn't add to the garage ceiling. Given the expensive and difficulty in adding to a finished ceiling. Have you checked the exterior walls and windows? That may be where a good bit of heat is flowing. Upgrading walls is challenging but you can work on the window. New window, storm window or the shrinking plastic.