Hi Atiful and welcome to the forum,
In regards to your first question, research is king in this game. Even when you find yourself in a position of having some level of sales success, you have to try and keep ahead of the curb by researching the market because if you aren't doing that, you've got thousands right behind you doing it and trying their hardest to take your market out from right underneath you the moment you take your eye of the ball.
Trust me, there is no business on the planet that is more competitive than e-commerce!
What and how to research, well there are multiple avenues to research. Product research, Supplier research, General market research, trending research (new products coming onto the market, new market trends and so on) So there is always some key area that requires a high level of research to even give yourself the best chance of success.
This is an area where most fail before they even start. Of course the Internet is full of garbage telling people how easy it is to make money selling online so many come believing that it's easy money. Well it can be money, but it's rarely ever easy money especially not now being how competitive the market is and that's only going to get worse.
In regards to bundling, I'm personally a big fan of that myself. I think that is a key marketing technique that can be used to get into the market, it can even be effective used against suppliers selling direct to customers through large platform like an eBay. So I like where your head is at with that idea straight up.
With the product search, just type the name of the product into the search bar and it will give you the results. You can then use the filters to narrow those results down. Now you'll find the top results will be the most accurate, they'll get less accurate and far more general as you move down the list of results.
If you find that you're not getting any results at all for your product search, then it could well be that we currently have no suppliers listed for that particular product. In that situation, just shoot an quick email to Link hidden: Login to view with your product inquiry and they'll see if they can find you some supplier leads to follow up with.
Just one tip in regards to bundling, it's much better if you can source from the one supplier. That way the customer gets their package at the one time, it doesn't come in dribs and drabs. That sort of thing can end up hurting you with customers as they get frustrated having to wait and your feedback and the chances of getting repate business can take a serious hit.