Foundation is The Base - Point A - the Starting Block of good makeup.
Skin does not have the qualities to let makeup stay on the skin. If you don't have foundation on, your blush color with wear off - or seep into your skin and be gone within a few minutes to a few hours. Same with eyeshadow (remember to apply your foundation to your eyelids.)
So even if you use a tinted moisturizer, start your makeup with a good foundation application.
How to choose a foundation? This is such a personal preference. If you don't need to wear foundation - i.e. you have even skin with good texture - then you may want to opt for a tinted moisturizer. Many tinted moisturizers have the added perk of an SPF. Even a tinted moisturizer will give your skin the ability to have blushes and powders to stay on longer and apply more smoothly.
If you need more coverage but don't want a heavy makeup look - try a foundation that has more pigment, and for a dewy look, find on with more oil in it.
A full-coverage creme will give you the base to hold a lot of makeup. Great for evening looks, a made-up look, or performance makeup for stage or film.
Why do professionals match your foundation on the jawline? The back of the hand or the wrist does not show the true color of your face. Although it seems easy to match this way, take the time to work with a seasoned makeup pro and get your foundation matched professionally.
We use the jawline as our match place because it will give an idea of how the foundation looks on the face, plus how it will look next to the neck. We are trying to avoid any marker of color change between the neck and the face. Be aware that faces may be darker because of sun exposure. Also, the face may be lighter than the neck because of sunscreen used on the face, but the neck still gets sun exposure. Get a good reading of what the makeup looks like on the face AND next to the neck.
Consider that the forehead may be darker than the rest of the face because the sun hits the forehead predominantly because of the face shape. It may be better to go a little darker so the makeup on the forehead doesn;t look to light..
Use a thick swatch of makeup while skin tone matching, and don't blend it in. It's easy to fool ourselves into thinking it is a match if we blend it in. If the swatch is thick and you can't see it in a mirror - that's a good match!
At MakeUpMania, we use all of these techniques when matching skin tone. We also consider the season. If the color is a bit too light versus choosing another a bit too dark - we may opt for one that is a little lighter if it is Fall and we are heading into Winter. Many people change a half to a full shade between Summer and Winter.
Even if you can't get a professional skin tone match - these pointers will help you when choosing your next foundation.