How to Use Concealer

Price has little to do with how good or bad make-up is. The formulation (what ingredients are in the cosmetics) is what's really important.
A concealer is something that should be lighter than the skin. Just apply it in spots that may be darker than the overall face, just like the dark circles or red blemishes or blotchy skin somewhere. Some people may never use concealer.

After applied concealer (if you need it), then apply foundation all over your face. Finding the exact color is what is the worst part. First, need a formulation right for your skin. Heavier foundation coverage might be for someone who had very dry skin or had plastic surgery or who was on stage. It could be used at night when there is no natural light. In my opinion, one of the worst things is to be "looked" like made up.
 
The salespeople can help you when you buying make-up in a department store. On the down side, they'll be pushing their products, whether or not the products are right for you. Also, these products are not at all cheap.
 
There probably are several different kinds of foundations.  The biggest problem is that there are rarely any testers. One thing you might check out is the store's return policy. If you get a color or formulation that just doesn't work with your skin at all, at least you can return it.