Is requiring Facebook login & offering discounts to users who sign up & their friends a good growth hacking method?

Hello all! We want to install some kind of growth hack referral model to our new project similar to groupon - online ecommerce web where users group together and get huge discounts if the goal is reached. Our products are Fashion clothes. We can offer 70% off retail prices. Our thoughts: 1) Let register with Facebook only. 2) We make a very simple way to invite facebook friends to our website. (don't know how to make it super simple yet) 3) We give a referral link to the user and he can share it for 10% discounted products with his friends. 4) if the user's invited friends buy, we give him additional 10% discount or $30 in cash to spend. Questions: How can we make this work? What would be the best way to engage users? Which model is better: 10 percent for the user and his friends or a fixed amount of $30? If anyone has experience on growth hacking, let me know and we can schedule a call. P.S. a good source of info about growth hacking would be much appreciated. Thanks!