Coins vary from 100,000 for $4.99 to 2,800,000 for $99.99, while diamonds will run you 200 for $4.99 to 5,800 for $99.99. Try the game and see how the default items treat you before spending your cash.
Atlas is an action-rpg with rogue-like elements where you use your ability to control the ground to fight the enemies and move through procedurally generated worlds.