Is my way of doing product research good?

I’ve tried finding items on Alibaba and looked them up on Amazon. The product category (home decor & improvement like carpets, kitchen stuff, etc) seems to be doing good & the product is in demand but the specific product that I chose on Amazon isn’t being sold.

Also, if I sign up for an individual seller account, how much product should I order just to test the waters?

When I order the product, do I just slap a universal product code, a big code on the case itself & ship it to warehouse? Should I ship it directly to the warehouse?

Also would I need to send the UPC and the code that goes in the case to the supplier if I want them to do the packing & ship it directly?