Finding the right foundation to suit you is very hard now days. There are so many brands and shades which can make the whole experience more confusing. Before buying your foundation , you need to know what type of skin you have. Does it tend to get oily or dry? When dealing with oily skin , its best to look out for foundations with words like like "oil-free" , "oil control" and "mattifying" on them. If your skin is a little bit on the dry side , look for words like "hydrating" or "moisture-rich".
When testing out foundation , make sure you have a clean fresh face and apply the foundation onto your jaw bone. Many people have this idea of applying it to their hands but our hands tend to be a different colour to our face therefore will end up with he wrong shade of foundation (and nobody wants that). I'd recommend choosing around 3 different shades of foundation and testing them all out in natural light. From there you can decide which one shows up the best or weather you need to change the shades. Most of the time, a foundation with a yellow undertone is best, unless you have the fairest of skin tones.
Finding the perfect foundation doesn't necessarily mean you have to cash out loads of money , brands like MUA and sleek have good quality foundation at affordable prices however higher priced foundation brands tend to offer bigger ranges like moisturising and sun protection foundation. Jut see whats best for you.