Ok, your question is too broad for anyone to be of real help. Let me try and narrow it down:
"Women's clothing" is a large niche - what keywords are you focusing on? e.g. "women's beanie hats", "discount designer brands"
Is the site your own or are you managing it for a client? If you decide what products to list, do your keyword research before stocking up on product.
Some quick ideas: look at fashion blogs, magazines etc: what topics are popular? what styles/celebrities are in fashion? Execute a social campaign based on trends e.g. "Beyonce seen wearing X jeans" then link to your sales page. Video sites and social image sites like pinterest and flickr are best because your niche is very visual.
Start a blog on your site and post regular content about fashion, celebrity and trends. Get lots of social shares for the content (you might have to outsource this to start with, or try free sites like addmefast).
With a strong plan and some hard work, you will hit your sales. Good luck.