Skincare is so important. You need to nourish it and keep it healthy so that it can do its job in being your body's first defense against the outside environment.
If you have really oily skin, your skin produces excess sebum that sits on your skin and can clog your pores. It might seem ironic but this may be becuase your skin is dehydrated. To make up for the lack of moisture in the skin, the skin produces extra oil to keep it moist. So the first thing you need to do is drink a lot of water! Hydrate your skin and body. Next, you need to get oil-free faces products, like face washes. It is critical that you get the gentle washes and exfoliators so that your skin's natural barriers aren't stripped off; this would cause your skin to be even more dehydrates and therefore make more oil. Make sure to use oil-free moisturizers and use them regularly. Keep your hands away from your face as well to avoid getting more germs and oil on your face.
If you have normal or combination skin, you usually get oily in your T-zone and dry to normal skin everywhere else. You can get away with using a bigger range of products but make sure to avoid touching your face too much and to drink a lot of water to preserve your skin.
For all my dry skin ladies, Your skin probably feels tight and crusty. What you need to do is use more oil-based products. Use thicker, cream-based moisturizers and face oils to add moisture to your skin. Like the other skin types, it is important to drink water and keep your body hydrated. I also recommend using hydrating gel face masks, they feel cool on the skin and your skin feels smooth and moisturized after. You should avoid clay masks, they tend to be extremely drying and will do exactly the opposite of what your skin needs.