If the colors are pretty; layers or punches or die cuts. If you have cheaper white card stock, I would use that to test out ideas before stamping on the "good stuff" or I let my son and his friends have some to draw on. Good paper matters and that cheap white stuff from Michael's just won't give you a nice stamped image no matter what ink you use.
Anything that just looks too cheap, so much so that you KNOW you would never use it on a card I would donate to a school or even a senior center.
Mary in NC