When I make a smoothie, I always start with frozen fruit. That way I don't need to add any ice to thicken it up!
It's easy to keep healthy smoothie ingredients on hand since frozen fruit doesn't go bad even half as fast as fresh so you can always have a healthy meal or snack ready to go in a few minutes. Throwing overripe fruit (especially bananas!) into the freezer is also a great way to cut down on waste.