It's always best to maximize sales on an existing product, before creating a new one. This could look like increasing traffic, trying to improve conversion rates, getting affiliate partners, etc. But start to maximize your time and investment that you created with the first product, and create a best performing funnel for all your sales. Once you feel your current product is selling at an optimal rate, it would be smart to create a product that is an upsell, downsell or crossell to the existing offer. And then follow the same outline with it to create maximum sales and traffic.