Without some distillation - this is a rather enormous question - as you're essentially saying, other than choosing e-commerce and a particular category - what does one need to do to start a business?

So, I'll choose to focus it down to what I always think is the most important thing to do at the early stages regardless of industry, approach, business model, or geography; idea validation.

TL;DR - Get off the lab bench - talk to your ideal customers - start to add value from now via a "proxy".

For those of you who have come across my answers here or elsewhere - you'll notice that I often turn to this advice; there's a reason - it's solid.

In your case - it's also something that you can start now - even while you are finishing up the MBA if your decide to allow that to continue to delay your entrepreneurial dreams (I'm half joking).

Start by identifying who your customers would be - how they currently buy what you'd be selling - and why they'd rather buy it from you.

Don't stop on the whiteboard - you'll get enough academic exercise through your MBA. Once you've developed an understanding of who you THINK your ideal customers are - talk to some of them.

Find out where they live online (you'll put this to good use again later when it's time to market in earnest). Use the conversations they are having online as a way to validate the pain you'll be solving with your solution. You can do some of this through mere observation - but you're far better off to join the conversation meaningfully.

You can also start to add value and build a following among the population. I spend a lot of time talking to startups and helping them determine a "proxy" for their actual business. You can often "start before you start" using something like a digital information product or a blog. I have some ideas specific to your case that I'd be happy to share.

By taking these concrete steps toward validating the idea now - you'll have a solid foundation to build upon, if and when your hypotheses pan out and you decide to launch your company. Until then - avoid the tendency to think of names, logos, co-founders, company HQs, ideal tech stacks, and the other 1,000,000 things that actually have to happen between now and you retiring a happy, fulfilled, and wealthy entrepreneur.

Enjoy it! It's one of the most exciting and important stages of starting any business.