Gran can be obtained by the Recycle feature. Each card that has a rarity can be recycled, which means starter cards cannot be recycled for Gran. Each card has a Recycle value based on rarity, the higher the rarity, the more Gran you get.
You cannot use the Recycler if the FILE editor is open in the Game Tab. To be safe, go to the Game Tab and return to the Game Home page before you Recycler.