I'll raise your tip with another: buy three sets of solid color sheets, two neutrals (grey, white, beige/tan, etc) and one bright/gemstone color (red, green, blue, etc).

Mix them up: one color for pillowcases, one for flat sheet, one for fitted sheet. Bonus points if you match to a three colored comforter.

Your bed will look like it's straight out of a magazine, you'll have rotating sheets like this LPT mentions, and you'll have an extra set just in case.