You only need 2-3 and possibly 4 marking pencils. And stay away from Yellow.
White and light grey Mult Pastel chalk Pencils. Possibly the Sketch and Wash black graphite pencil (all from General Pencil Co) and the ceramic mechanical pencil in white. And of course a good old #2 or better #2.5
And the wash out pen.
To me all the colors are a waste of money.
And keep them sharp. I mark about 13" and hit the sharpener.