Depends what you're looking for. You can get anything from Amazon, but I like to use redbubble to shop since it supports creators, not companies.
Ebay is good for interesting cheap shit. Facebook marketplace is good for cheap and free usefull stuff. Amazon is good for a cheaper option than most things. Craigslist is fucking amazing in my opinion. It has some good free shit and for most things, they have good prices. A good mobile app is OfferUp Everyday, I go through OfferUp, Craigslist, and Facebook Market
I use all for different things. Keep in mind I'm a frugal son-of-a-bitch. Amazon if I really need something new. eBay if I'm looking for parts for my car (since Audi parts are cheaper to import from Latvia/Bulgaria/etc. instead of the dealership). Also use for used parts for computer, iPhone, or buying a used tech device. Facebook marketplace for buying a used car. No one really uses craigslist anymore for cars since they require a $5 fee to list a car. Facebook groups are really good for cars and parts exchanging/discounts. Facebook groups for anything else too like computer parts, clothing, etc. Get some good deals (but you can't lowball since people in the group know the true value of a product) Never really use craigslist at all. I tried it but never could find what I wanted. Only really good for looking/buying classic cars.
