If you want higher profit margins and generally less amount of sales, don’t use Amazon as a supplier. It’ll be less competitive. However, you’ll have more challenges concerning customer service, returns, shipping,etc.
If you want smaller margins and tons of sales to compound, use Amazon. You’ll have less challenges concerning customer service, cause they are the best. Competition is fierce.
Generally speaking, you want to stick to one main supplier and use others as backup if main is out, don’t jump to too many suppliers. Pro tip: Choose products where multiple suppliers offer it so you have options when you are out of stock.
Make sure you have some sort of way for cash back, whether it’s discounted gift cards,credit cards, or websites like eBates. Those help you make more money.
Shipping and handling
ONLY offer what you can deliver, and Amazon’s metrics gives you more visibility. Fast N free option is great for more visibility if you are using Amazon, if not, forget about it.