The ingredients I typically use are bananas, avocados, melon (either watermelon or honeydew melon - whichever is on sale), and berries (blueberry, blackberry, or strawberry - sometimes all three, again, depending which ones are on sale). I don't measure it at all. If I want more of a berry flavor, I'll add a larger portion of the berries and decrease the melon portion.
Occasional ingredients I use are mangoes (usually yellow mangoes if they are available), kiwi, applesauce, organic spinach, tofu for protein, pineapple, and peaches.
Then, once I've added the fruit, I try to added either chia seeds or flax seed meal, agave nectar, fresh squeezed lime juice, and once in a while, raw cacao powder. To thin it out I add some water, up to the quarter level for the blender or canned coconut water. I may also add canned coconut milk if I have it around. For vitamin B12, I add a tablespoon of nutritional yeast.
I don't use protein powders. If I want protein, I'll add extra tofu which works fine. If I make too much, I'll store it in a glass or container for later in the day. It's very simple when you have the ingredients in your kitchen and it makes each day start off on the right foot!
See my simple smoothie recipes