Make sure to follow the walkthrough video if you're stuck on an important client. The wedding dress requires you to purchase the "fitted satin" top style, as well as the "mermaid" skirt style.
As for crashes. Your PC should have at minimum 4GB of RAM to play. The game is already optimized so that it doesn't take up nearly as much memory as before. Further optimization for lower end PCs is not possible. Just try and make you have nothing else running when you're playing Tailor Tales.