Do I need to have a website to sell items for my brand in Amazon and some social media sites such as Instagram?

I am planning to sell luxury home goods and eventually beauty products online but I don't have the physical products yet and I am having the dilemma of trying to create a physical site since I don't want to spend the money only for my items to not be sold. Instead I was thinking once I get my physical items, I would create a Instagram, Facebook, and Amazon page. Once I get a good customer base then I can use some of the money to create my physical site because this whole process of trying to create a site and not even have the products yet is driving me crazy. Do I need a site to upload my items into these sites or do I really need to create a site?