Is there a Stack Exchange site where users can ask questions about skin care, cosmetics and beauty tips for both sexes?
If you are looking for tips using common materials not specifically designed for the purpose, Lifehacks.SE will work for you.
If you want to know what chemicals are used to achieve certain results, you might try Chemistry.SE
If you are just looking to find a good beauty product, this probably does not belong on any currently existing Stack Exchange site. That said, I recently answered this question by a user asking about expensive electric razors. If you want, you can talk to them and create a new Stack Exchange site for beauty and personal hygiene products. If you have a specific format for how questions can be narrowed down so that they aren't too open ended, you can suggest a site on the Area 51 page.