Can you please share a bit more details about your product (your country of origin, prospective markets, etc.) so as we can provide you with some at least basic answers. They can vary substantially depending on this.
Although most of us have some great experience when it comes to online marketing, I don't think you are going to find the answer you are looking for without talking to a tax consultant around your area. I hate this time of the year LOL time to find out how much I owe Uncle Sam.
A Tax consultant will let you know how much you need to make before it can be taxed as well as what you can deduct.
Ecommerce presents a major challenge role in the administration of different tax challenges, whereas if you want know about the sales tax then it is a tax which is levied on sales of goods. I think in India sales is levied if you purchase anything from online store.