I have about 7 month experience with facebook ads and shopify. I've had decent success but hope it will pick up faster soon. When you start LLA's you need to be active everyday in creating new ad-sets and kill those who have low (cpm) or just are not successful in general. The best strategy to date seems to be to start a PPE campaign and start running LLA's after gathering som data (about 100k views), then run LLA's for 75% VV, 95% VV.