Monday's Riddle! The Grand Prize!

Hello Riddlers! Here's this week's puzzle. Can you guess the theme?  ; ) ~ F

Hold your breath and grasp me tight-I'll get you in when the time is right. Come inside for just a spell- promise that you'll never tell. For all the world cannot know, just the ones that make the show. I will shine and shimmer gold, always lucky to whom I'm sold. When, at last, you've made it in, my worth is judged by what you win. 

What am I? 

Here's a clue!