There are so many because it is a very lucrative business! Have you been into a Sephora? So many brands, it can indeed be overwhelming. They tend not to carry the 'drugstore' brands, but opt for more expensive items. Nothing wrong with the drug store brands, I say!
Most cosmetics departments have beauty advisors, so next time you are in, just have a chat with one of the sales advisors, and they should be able to assist. Makeup and skincare does not need to be terribly expensive, and it can feel like a treat.
Instead of traditional foundation, which I always found too heavy, I use a tinted moisturizer with sunscreen. They can be found at all price points. the brand I use is Canadian, so most likely not available to you, Boots should have No.7, which has a version, at a reasonable cost.