I carry a level and two bags of the plastic leveling blocks. My standards are fairly low about perfectly level.
Most commercial RV park sites are reasonably level and take minimum or no blocks. Many rustic govt sites take more leveling. If many sites appear unlevel, I scout sites and try to select a level one if it is decent otherwise. I usually can get it reasonable with up to 3 inches of blocks in low areas as required. If it is within half bubble i'm generally good with it. As mentioned it just has to be reasonable.