With two "Kelbi Horns" in your item pouch, speak to the "Guild Sweetheart" at Moga Village. Select Low Lv one star "Prescription Pick-up" gathering quest and deliver the two "Kelbi Horns" right away. Once the quest is complete, take the 2 "Kelbi Horns" from the reward box and sell/collect the rest of the items. You'll received 800z for completing this quest. Repeat this method to receive more Zenny.