There are many ways for you to acquire in-game currencies through the course of playing Super Spell Heroes. Both Gold and Gems can be acquired from Chests at the end of Battles, or found along the path while progressing through an Area.
Gold and Runes can be obtained each day from the Celestial Emissary.
Gold and Runes can also be purchased for Gems in the in-game Shop, while Gems themselves can be purchased with real-world currency.
At several points throughout the game, it is also possible for you to earn additional Gold, Gems, Runes, or Keys by watching videos.