At first I was going to recommend not going for a one-product site. Then noticed you've already started building it. The main thing is - successful one product stores are a lot harder to build for beginners. There's a very small margin for error. Being a beginner, you won't ever be sure whether you've got a winning product on your hands, if your marketing/ ad targeting is on point or if your website design is the best it could possibly be. And it's already your 3rd store, which for me looks like you're developing a tendency to quit easily if you see negative results. Normally, people who build successful one product stores already know their way around the business. Anyway, I wish you good luck and will be watching your progress.