Those gel crystals can be found in diapers. Though I don't know which is cheaper. Always had success with old sponges mixed with a less peat based soil. I've re-potted plants after 3-4 years to find the remnants of sponges that I had forgotten were integrated in the mix to begin with. My favorite has always been filling up Coca Cola bottles or other glass bottles and inverting them into the containers soil. May your plants never go thirsty. And you as well.
