For gameday tailgating you'll have to either park on the street or a private lot. There's usually spots available on the side streets and next to Sheetz and the alley behind fast food places south of 5th Ave. The firehouse on 20th St and Marshall Child Development Academy allow tailgating for a donation. There's also on-street parking in the alleys and roads behind Tic Toc and other businesses, north of 3rd Ave.). The university lots and most private lots (Tic Toc, University Car Wash, fast food places, etc. are permit only and sell out by early summer).
And be aware that you can't tailgate at the ACF lot, it's for parking only. I really hope that once the transfer goes through, it will be available for tailgating but we'll have to wait and see. And it's absolutely crazy how many people buy spots in the West Lot and either don't use them or arrive 20 minutes before kickoff.