It’s said that boards made from densely grained woods like oak, maple, and hazel house spiritual energies better than cardboard or plastic, and that constructing a board yourself will attune it to your vibrations and make it more effective. People have successfully contacted spirits using anything from the store-bought Hasbro version to a piece of paper with letters drawn on it in Sharpie, though, so the limiting factor is probably in the technique rather than in the material it’s made from, assuming you’ve minimized friction between the planchette and board.
Personally though I really like using the wooden boards I’ve bought and made–they just feel nicer to work with and more “real” if that makes sense. Using a cheap plastic version that you bought for $19.99 at Walmart just feels like you’re playing a parlor game, and with that set and setting your results will probably match. Compare with taking the time to design, craft, etch, and stain your own board–an involved process and something that helps set your mind on the serious task of spirit communication you’re engaged in. 
Yeah, I’ve read other sources that say it’s best to use a male and female working in tandem, or at least have the polarities expressed in both partners. J. Edward Cornelius in Aleister Crowley and the Ouija Board says “a ‘positive’ medium receives the message through his or her brain and transmits it to the board, while a ‘negative’ possesses the driving force–I mean that, apparently, one sitter supplies mental, and the other muscular power.”
My beef with using more than one person is that it’s hard enough for me to control my conscious thoughts that so easily manipulate the direction of the planchette; multiply this by everyone using it and you have no guarantee you’ll receive anything legitimate. The juego de la copa sounds pretty cool though. I’ve read accounts of people using an inverted glass in the same way but haven’t experimented with that type of planchette yet.