Serums are an ideal way to get potent skin specific ingredients into the skin fast!
They can range from liquids to lightweight creams and even oil textures. Serums reach deeper as well as quicker into the epidermis making them a perfect pre-moisturizer step. The reason why serums are usually more expensive and in much smaller packaging than a jar or tube of moisturizer is because the efficacy is so much higher and concentrated ingredients are harder to stabilize. So it's safe to say that serums are usually one of the most important and higher priced items in your routine. Applying a serum before a moisturizer is like flossing before brushing the teeth. A thin layer (remember serums are highly concentrated) all over the face, neck and chest is ideal and we need to remember those areas when treating our skin with any product, including cleansers, exfoliants, etc. Occasionally people won't use moisturizers over a serum depending on how much oil is in the skin and/or during warm, humid weather but generally speaking every skin can do well with some form of a serum underneath a daily spf moisturizer and under a nightly moisturizer.
Some examples of my favorite serums:
Vitamin C hydrating serum (mature, sensitive skin, thinner skin, rosacea)
A C E liquid serum (thicker skin, aging, sensitive)
Iluma Bleaching serum (hyper pigmentation)
Pure Hyaluronic serum (dehydrated, pregnant
Glycolic serum (anti-aging, firming)
Clear Cell Restoring serum (acne, dehydrated)
Resveratrol Lift serum (lifting, mature, sensitive, pregnant)
Premier Cru 1/2 oil 1/2 serum Elixir (anti-aging, nourishing, any skin)
Vinoperfect Brightening serum (hyper pigmentation, any skin)
SOS serum (sensitive skin)
Overnight Recovery Oil (dry, sensitive, aging, pregnant)
C15 Detox Oil (any skin)