I only buy from websites that control their own supply chain -- meaning they know who they are dealing with when they procured the goods, not randos from overseas.

I love Target, free shipping threshold is $35 but you get what you ordered 100% of the time. They have a good selection for most of what I buy often. You can mail back returns or take them to a store. I like Microcenter for electronics.

I also buy from brand websites directly, since they have no reason to send anything but their authentic products. Brand websites often have deals. Join the mailing lists of your favorites, a lot of them send out discount codes.