If the weather is good, the Johnson Park lot across River Rd from the Stadium will bo open (it isn't open if the field is too muddy). It is the closest lot with game day parking. But it typically fills up 2-3 hours before kickoff. This lot is very popular with visiting fans. The other popular lot is at the Greek Church a couple hundred yards down River Rd. I think the chuch may have some tailgating restrictions. The other gameday lots are much more subdued.
If you want a taste of Rutgers fan tailgating, then you would need to buy a pass for one of the season lots from the secondary market. Season lots fan out in a northward direction from the stadium in the following order: Scarlet, Green, Yellow, Blue, Purple, all the rest.
Scarlet has the oldest and most well-heeled crowd, followed by Green. Yellow is the largest lot and has a mix of older crowd, family, and younger crowd. Blue, historically has been the wildest lot, but recently has toned down a bit. And Purple has picked up its game as cost has forced some fomer Blue-lotters to Purple. Beyond Purple, tailgating is a mixed bag and many passholders for those lots just park and then join friends at larger tailgates at the closer-in lots.