When you get the Chief Fisherman's' Daughter, go to the beach where she goes to find the Aquamarine. When you fight the little Jewel Leapers. they give you the stones that are needed to make Runes. Get a large number of them and some gold, then go to the Rune-Makers shop. You will want to Refine those Gems into Runes, which cost 230 gold. When they are refined, the Rune Shop will buy them back at 400 to 500 gold.