I haven't made any green smoothies in a long time. I used to put in spinach, raspberries, and stevia. I'd use about a cup of frozen spinach and 1/4 cup raspberries- any more fruit than that and it would mess up my blood sugar. I'd add rice or egg protein powder if I had it on hand, but since those are rather expensive, I usually had them without added protein. I'd either drink it alongside some hard boiled eggs, or I'd have it for a snack rather than a meal.
I think I remember when I stopped having the green smoothies. When I got my secretor status verified and I realized I shouldn't have the stevia. I couldn't ever get used to the taste of it unsweetened, and any other sweetener led to blood sugar swings.