The biggest obstacle in any sale is trust, and the quickest way to build trust is to give. If you are a brick and mortar retailer, the best way is to give away free samples.
But in e-commerce, you have the shipping cost. So the best you can do is to create a free plus shipping offer where you offer the minimum number of product for free but charge for shipping and handling. If your cost of goods is negligible, you may even make a small profit on the free plus shipping offer.
Islamic Principles Website 