To make this shirt, you'll need the following:
Purple lace (I got a yard and a half for a large shirt)
Cut the lace into strips and lay it out on the shirt in the pattern that you like best.
Lay out your rhinestones in a pattern that looks best to you. I decided to vaguely follow the shape of Rarity's cutie mark (though I know it's hard to tell) and put some of them under the lace so that little shine peeks through.
Iron on the rhinestones according to the package directions. Make sure that the iron won't melt your lace!