Here are some sites for reviews, and tips.
Makeupalley: A site where people rate and review products. There is almost not a product you can’t find. I almost always check products out on this page before I buy them.
Temptalia: It’s a blog site with some really cool features. With the community’s help, you can find suggestions for dupes and your colour/shade of a certain foundation. So fx. I’m a MAC NC42, then I can get a list of shades I am in of other brands. This has helped me a lot as I order a lot of my makeup online.