I do a lot of craft shows,
I usually use mid century stainless steel trays and dainty holders (think Kromex salvaged from garage sales and thrift stores) to display my buttons. I find people like to dig just a bit to find the perfect button. I sort them by types, words in one, maps in another, vintage kids books, comics etc etc
for me it all fits into my reuse recycle upcycle theme
I personally don't card my buttons individually as to me that is an excessive use of paper that may or may not be recycled and I'm not comfortable with that
I have seen other crafters put their buttons onto bulletin boards or clothe stretched items like picture frames, screens etc so the buttons display in a single layer
there's a picture on my blog in this post
http://periwinkledzyns.blogspot.com/2011/04/vincent-massey-unesco-conference.htmlGood luck Stacey!