Frankly speaking, growth hacking is much more than offering discounts or freebies.

1. Facebook login is required, because you can straight away take them to your Facebook page and show him what you got. If he or she finds the clothes interesting, they would anyway buy. They wouldn't need a coupon or discount. If they don't like them, they don't buy even if you offer 50% discount. The philosophy of discounting is getting outdated. The in-thing is to make it relevant and offer the right price, so that he makes that decision right away. The relevance can be targeting the right audience. Don't waste money on carpet bombing. Identify your target segment and run focused campaigns by following your target clients.

Engaging your prospects is the key. If you are targeting premium clients, have a cozy blog with interesting articles, tips, HD pictures, etc.

You could go thru couple of my articles that could open up some of your thoughts in this space.

https://www.linkedin.com/pulse/paradigm-shift-sales-shivadhar-soma?trk=mp-reader-card

https://www.linkedin.com/pulse/honey-shrunk-marketing-campaigns-shivadhar-soma?trk=mp-reader-card