Regarding Online store ...

Hello Sir, I am Shubham jain. I want to open an online store, where I'll be selling goods online (preferably accessories). I want to know about what things will I be needing to start the store. Now at this point, since I don't know about how my store will work and the response I'll get, so I would like to check/test the market and response only after that I want to get the registration done. I don't know about the procedure that needs to be followed in India so I seek your guidance and direction. Can you please tell me about what all documents/formalities that will be needed to start ? Also can you please tell me if I do not get the business registered in the starting (test phase) and I'm not the manufacturer I will buy the goods from someone who is manufacturing them, so in case of a non-registered online store can there be any problem that someone will ask me about the bills from whom I am buying the goods and selling because I don't think that they are also having registered firm because their business is running at a very small scale. Another question that comes to my mind is about the VAT, UP VAT, CST, what are all these things and what is needed if I sell and send/buy things from other Indian states ? I am from a science background so i don't have any knowledge of all this. I request you to please guide me like how to proceed ? I will be highly obliged to you please help me with your support and guidance. thank you so much waiting for your reply Regards, Shubham Jain