It depends what I'm looking for - if I'm buying stuff like collars and pieces of wearable things, I'm rooting for eBay. Everything is so cheap, even thought it takes a long time to get where I live. Amazon is a good place to shop for those products too, also internet thrift stores. You can find some good things for a low price if you just keep looking!
What it comes to food and all, I'm rooting for the things you get from the pet store. I've tried getting some food for my dog from the convenience store but my little lady doesn't approve that much what it comes to the brands that are sold in normal stores, haha! Well, what ever for my spoiled baby!