Help me create an attractive instagram sweepstake poster for my small business

I need help in creating an attractive instagram sweepstake poster for my business with nice graphics. Sweepstake is to win a free custom black wedding dress from our collection up to $2350 in value. Will provide logo and pictures ( attached) . If any additional content is needed i can provide that after the basic design is done as well. I want the instagram dimension poster to be really attractive because I want it to help me get more exposure . ( Website is www.bridesandtailor.com)