I would say using a diff moisturiser day and night is essential, as you need an SPF for day, but you really musn't use an SPF at night, as it's really not very good for your skin (just a lot better than getting skin cancer etc)
Serums work well if you feel you skin is in need of more moisture than your day cream gives you, and eye creams are for you if you have fine lines around your eyes and on the top of your cheeks, as these are usuallyl caused by dehydration.
I'm a total Dermalogica addict, and if you do decide to use their products, it's worth going and having a facial first, as all their 'people' are really well trained and able to tell you exactly what to use for your skin.