Best way to have a lot of Clay is mantis + horse, go to the desert, give mantis axes, jump on it, and start destroying cactus and rocks. (with axe you get lot of sand and cactus sap) when your mantis heve to much weight, dimnount it and give everything into horse that is following you. (Horse get - 80% weight to sand, cactus sap, and clay) Start crafting Clay in horse saddle, jump back to your mantis and repeat this whole proces. Happy gathering:)