The best bargellos I have seen are more about value(light, medium, dark) and the skillful placement of the values in the strip unit then about color. I think you would do best to select from your scrap piles based on tones of light medium and dark and once you have about 20 1/2 yard pieces picked out then start arranging them in the order you think they would look best prior to cutting any strips. JMHO.
Edited to add, google images of "scrappy bargello quilts" and you will get loads of ideas.