Adding a gift with purchase can help increase your average order value (AOV) by incentivizing customers to spend more to reach the qualifying threshold for the free gift. For example, if you offer a free gift with purchases over $50, customers who were planning to spend $40 might be more likely to add an extra item to their cart to qualify for the gift. This not only increases the AOV but also introduces customers to more of your product range, potentially leading to future purchases.