Leveling blocks (pieces of wood or those plastic Lego levelers) :
Leveling your trailer is done side to side by raising the tires on one side or the other, and front to back by the tongue jack.
There's going to be campsites where you'll need something under the tires on one side or the other. I carry a couple five foot pieces of 2 X 8, with the ends trimmed for making a ramp, and a some shorter pieces (12 - 16 inches long) for use under the tongue jack.
Your stabilizer jacks are for stabilizing, not lifting, and work much better when not fully extended. I carry some of the plastic blocks to stack, as needed, under the stabilizers. Short pieces of 2 by's will also work for this.