The biggest mistake someone with oily skin can make is not to use moisturizer! That is because the cebaceous glands tend to overproduce oil to compensate for the lack of moisture. Your skin will continue to look oilier every time you don't add moisturizer. The main reason is that skin is hydrated primarily from the outside rather than the inside.
Moisturizers for oily skin tend to feel really light weight and seem to vanish quickly after application. If the moisturizer is feeling heavy, it is likely the wrong kind for your skin. Now, if what you are looking is to prevent wrinkles, the best anti-wrinkle ingredients are sunscreen, retinol, glycolic acid, peptides, and acetyl glucosamine.
Another mistake I see people with oily skin make is they over-wash their face. They think that washing four-times per day will get rid of the oil. Overwashing disrupts the skin's delicate moisture balance, leading to irritation, sensitivity and potential flare-ups of conditions such as eczema. Skin can produce more oil following over-cleansing, creating a vicious cycle of excessive oil production.
In addition to a harsh cleanser stripping skin of the lipid barrier that keeps skin balanced, water itself is actually very drying because it draws moisture out of the skin. I recommend using a cleanser that is right for your skin once or twice a day maximum and then rinsing with warm water to avoid stripping skin of its natural moisturizing factors.
Some great mk moisturizers for oily skin are the Botanical Effects Formula 3, Velocity Moisturizer and the Timewise Moisturizer for combination/oily skin. See the website for more details. www.marykay.com/anabelbeauty