Go to a lumber store, buy you a 2x12 or two, and cut it up into a bunch of squares. Throw a bunch of them in your outside storage.
When you first get to a site, check how level you are before turning on the hydraulic jacks. If you are way off level, set some blocks up and drive whichever side is lowest onto some blocks. Get it as close to level as you can with blocks, first. Use rest of the blocks under the jacks to limit how far they have to extend.
I don’t like to ever lift any wheel off the ground, front or back. Can put too much lateral stress on jacks, and makes the RV more shaky inside. Tires (all of them) being on the ground (or on blocks) gives you more lateral stability.
Oh, and expect that every so often, your blocks will crack and become firewood. That’s why you cut up several blocks, so you have some spares when that happens.