Generally speaking, smoothies are good for you, as long as you stick with natural ingredients. You can put in anything you like – fresh fruits, berries, spinach, kale, etc. Depending on any food allergies you may have, there are many options for the liquid portion such as soy, almond or coconut milk or regular milk.
There are hundreds of recipes online for making smoothies for all occasions – pre workout, post work out, energy boost, whatever. The key is using ingredients you are not allergic to (if you have any food allergies) and portion size.