I've been in amazon for a years working with my friend's position as a supervisor, before i become a supervisor i was a Lister which is the reason why my client gets interested to me, I list or research product based on my standard that i am pretty sure my clients would like it. For example, based on there stars and reviews, also with the price like 20-60 usd, that is the Price where everyone would purchase because it was cheap. After the listing, you will add to amazon seller central as a merchant, we compete to other seller so we should be on the right spot like 1 - 3 spot. better on the first spot, and win the buy box. i can manage inventory, by checking there stocks using e-comm and changing there prices using appeagle, i also use this tools for searching like, jungle scout, merchant words, Priceblink and etc. i also knew FBA on amazon. searching product which is not on the amazon and list make, make our own title based on the suppliers and the descriptions i can list 15 items or 20+ a day but it still depends on the profit margin, because the higher the more harder to search for good listing. i am also expert and excel on google sheet.