I took some Cokin P filters out for walk last week.
Graduated ND filter to hold back the sky, ND4 and ND8 stacked + a graduated orange to add some colour into the sky which was red-ish but not exactly vibrant. Slight PP in LR4 to add a strong contrast a curve and a minor tweak to hold back the magenta cast my filters add when stacked.
The cheap ebay Cokin copies I have are ok, they do add a magenta tinge, most annoying however is the lack of labelling. I spend ages squinting through them to ascertain which grad is which. Really that shouldn’t be an issue, pick one , meter, use it, check histogram.