I love smoothies. I drink one almost daily.
Here's how I make mine.
I start with either milk, juice or homemade yogurt. You can use storebought yogurt but I find it too tangy for me.
Then if I want greens in it, I'll put a handful or two and hit the liquify button. This makes it smooth with no green chunks!
After I've added the greens to it, I add FROZEN bananas to it cut into one inch chunks. If you add extra ripe bananas you won't need any sugar in it. It will be plenty sweet. Set to blend until smooth. I usually add 1-2 cups yogurt and 2-4 bananas. If you use frozen bananas you won't have to dilute your smoothie with any ice to make it thick and creamy. (The blender I had at the time of writing this was an oster. It cost me around $30. I used it for over a year and it still works. )
Then, I add whatever frozen fruit I want whether it be frozen blueberries, blackberries, strawberries etc.