Your second option would be to use water to climb up their tower without wasting blocks or worst case use lava and a fire resistance potion/God apple.@AboodPlayz there are kits that provide bows, but that doesn't guarantee that you can knock them down. They could be building up a corner, or you can just be terrible with a bow.
I cannot really argue or agree since I don't play duels often and when I do, I play with certain kits.