Place blackberries, half of the ice, and 1-2 tablespoons of sugar in your blender. Pulse until smooth. Pour into serving glasses.
Rinse out your blender. Add mangos, the rest of the ice, and the remaining 1-2 tablespoons of sugar to your blender. Pulse until smooth. Pour into serving glasses on top of blackberry mixture. Serve immediately.
Notes
Add 1/2 cup blackberry yogurt or Greek yogurt for a creamy smoothie.