A great makeup look begins with good skin, so make sure you're looking after yours. Develop a cleansing regime and stick to it, and if you find you're having trouble with acne, rosacea, or any other skin condition, don't be afraid to visit a doctor or dermatologist for advice. There's no need to suffer in silence.
Then, prep your skin before you begin applying makeup. Ideally, you should moisturise a few minutes before applying makeup, giving your moisturiser time to sink in. Moisturised skin will hold product better, without dry, flaky patches. If you have oily skin, don't skip this step, just use a light, oil-free moisturiser.
Also, consider a primer. They may seem like an unnecessary extra step, but not only can they target specific skin concerns (like excess oil or redness), but they also create a perfectly smooth base for makeup and help extend staying power. Eye primers have a tint and work like a foundation on the eyes so colours appear brighter and more even, brilliant if you're using a bright or light colour.