To set up an efficient budget, calculate the cost of customer demand generated by your promotion. For instance, if your tailored promotion targets an audience of 100,000 repeat customers with a 10% discount and your brand's average order value is $30, the minimum budget calculation would be: $30 * 10% * 100,000 * 5% = $15,000. Avoid setting unrealistically low budgets for substantial discounts to prevent budget overspending during high-traffic events.