My favorite is collard greens, raspberries, and pineapple.
I'll add some type of oil, and sometimes protein powder if it is my entire breakfast.
I grind up oatmeal in the coffee grinder, then soak it in water overnight to make an oat milk beverage. I use that oat milk as the liquid. Tons of fiber, and it helps the smoothie last me through the morning. Otherwise, the sugar burns fast and I'm hungry about 1 1/2 later. My blender works fine to blend everything up. I'm not raw vegan, so I'm not sure if the oat milk adheres to the dietary standards.
I freeze grapes when they are getting too old to last too much longer in the fridge. Add them to smoothies that aren't quite sweet enough and they'll sweeten it up for you without having to use sugar or another sweetener.
If you're just starting, or for somebody who's not quite sure about the whole green smoothie thing, I suggest baby spinach and swiss chard at the beginning. They don't have strong flavor, and you can begin with small amounts until you see what you like. Kale, collards, and the others are not for the feint of heart.