When planning what craft or crafts you want to try at your Pinterest party, you should look to your guest list to point you in the right direction. Easy crafts set the stage for a more social gathering, which better accommodates a larger guest list. But more complex crafts, or ones with lots of pieces that take up extra space, would probably work better with a smaller group of four to six. Think of it like a game of Monopoly -- the fewer players you have, the more likely you are to finish the game.
Also, you'll want to consider the outcome. Are you looking for a craft that will help expand your crafty skills? Maybe something that your guests will be able to use? Or just a fun way to spend an evening socializing with friends? If you have a bunch of people coming who aren't terribly crafty, then you'll want to pick something simple and achievable. But if you're hosting the ladies who are dangerous with felt and a glue gun, then go ahead and choose something out of your comfort zone. Be sure to make a supplies list ahead of time and figure out what you will provide and what others need to bring. You can include that information with the invitation.