GST Registration Query for Online Mentorship Classes and Courses

I am planning to start an Online Coaching Business on my own with no capital as such. I will be providing mentorships to students and also there will be certain skill based courses which I want to sell. I am the instructor of those courses as well. I don't want to start by incorporating a Pvt Ltd or Partnership. I am thinking of starting as an individual and get a Trade License from the local body with the address where I currently stay (it is a rented apartment in Kolkata, West Bengal). I will just make an website and market it as per my capability to get some traffic. I am hopeful of getting students(customers) from other states as well. Do I need to get a GST registration before even starting this thing? If yes then what are the documents required and what is the timeline of getting that done, because I want to start real quick. If no, then when shall I register for GST. Will it cause me any problem in the future. Also if I end up doing really good in short time, then I would also want to save taxes. At that point of time is it advisable to continue as individual/proprietorship business or to get registered as a company? Really need clarifications on this.