Hello, I have a site of product sales for women. Shall I add a free directory in my site, to get more inner pages, and more links to the homepage ? Will that be any good for my SERP ?
Yes, but make it on topic. Not general directory, but directory that is closest possible to the topic of your website. In other words, no link farm, but useful resource.
You can do many things, it's only up to you. Even harder to say when one doesn't know even a tiny bit about your site. Generally, I would say writing articles might be better investment, but, if you are very serious about that site, the best thing is to do all that you can, anyway.