Launching your product when it's ready is fine, but it must be done correctly. You can't expect to make sales immediately upon launch. First, establish brand awareness among potential customers, and then devise a strategy to encourage them to purchase your product.
The only way to get customers is to build a product that solves a problem, and meets their needs. You can’t build something and hope that customers will come. You need to first understand your market and build something they would actually want.
A lot of startups just sell their products, without thinking about their business model. You need to work out your revenue model. How will you make money, and how much can you actually make?