We launched our project last Wednesday, and so far we've raised 25% of the goal.
We spend over $10,000 on the Facebook ad, good ad, and youtube ad within the past four days, and conversion rate is really low. So far, none of the backers from one of those AD! Most of our backers from friends, and followers, and they refer us the rest of backers.
From our experience, the best way to get more backers is to build a larger community before launching, asking feedbacks from followers, friends, and people who like your products. If you are only spending money on Facebook Ad, but skipping the steps to become friends with them online. You are just wasting money on ad, because they won't back you as a stranger.
Our Project:
https://kck.st/2II9JXB