Simply make every step of the riddle have potential to give an item.
Like when it asks to to find the 3 skulls on the sticks there's a chance for 1 or all of them to turn into a skull that can be turned in
if it wants you to find a grave you can dig where the grave is after you solve that part of the riddle and get one of those little relics that glitter on the beach
etc etc after that
This idea also makes riddles with more steps more rewarding, so solves multiple issues at one!
