During my (still active) funding campaign for SQUIDS IN I offered a couple of giveaways. First was a raffle where I would gift three cuddly octopuses from Finding Dory to those who had pre-ordered. The second was gifting octopus stickers for every new pre-order (provided I was given an address).
I don’t feel these efforts gained me more followers/orders but it does show your willingness to invest in your own project and should therefore encourage others to do likewise.