You want to find a product that is either wildcrafted or organic and has no fillers, binders, or anything else. Just pure herbs, foods and/or algaes. After doing tons of research and trying countless products, I found these to be the best and most nutritionally dense:
I usually just blend those three in larger quantities myself. They are by far the best green powders-- literally the most nutrient dense foods on the planet. Just by mixing one or two of them teogether, they are as good as the super expensive complex blends you get at the health food store. Plus you need less and it ends up being cheaper. Just my two cents : )