https://wisemerchant.com/blog/high-roi-facebook-ads-list-build-ecommerce
Brilliant case study from Wise Merchant on how Wee Squeak grew an email list using facebook ads.
Step 1. Create audiences based on interests and exclusions
Step 2. Create Lead Ads to capture emails
Step 3. Split-test Lead Ads by audience to reduce costs
Step 4. Automate costs with rules