How do I create first-order discounts for subscriptions?

I'm running an e-commerce subscription business and want to create attractive first-order discounts to incentivize new subscribers. I need strategies that not only encourage initial sign-ups but also ensure long-term customer retention. My goal is to design a discount approach that feels valuable to customers without compromising my profit margins or setting unrealistic expectations for future orders. What are the most effective methods for structuring first-order subscription discounts that balance customer acquisition with sustainable business growth?