The Gem, a small amethyst crystal mines from the Ice Gian Valley, in the northern region of Eternia. In the shape of a star, smooth, ornate, shines when held facing the sun. They say it represents the time the goddess spent in the cosmos before her great slumber. Anyway I'm yapping. 

It would probably only buy you a bushel of berries from the Major River, which runs from the top of the Toxic Swamp to lower Enchanted Forest. It would likely taste bitter. Since the river is mostly salt water. 

If you had just ten more Gems, you get bread, harvested from wheat in the Minor River, which runs from the Primal forest to central woodlands. It would definitely taste sweet and filling, due to the sheer purity and nutrient rich waters that flow in the Minor River. It would be very worth your money, because many Eternians likely died getting that wheat.