We've talked about them before on The Penny Rose—the facial oil/serum. How to choose? Which one is the best? Who likes what, and why? They're all something of an investment, but as a long-time user of facial oils/serums, I've noticed a remarkable difference in my skin when I'm using this extra form of moisturizer. All of the above have different ingredients, but I've used them all and I feel like each one pretty much does the same thing. I will admit that the most expensive option, the Rodin Olio Lusso, does work the best, at least on my skin. In short, a face oil or serum provides an extra layer of deep moisture to your skin. The side effect is that it gives your epidermis a sweet day-long glow, too. For an inexpensive trial version, check out the Josie Maran Argan Oil in the .5 ounce version for just $14 at Sephora. It will give you a good sense of whether you're comfortable spreading oil on your face. And acne-prone girls, don't worry, none of the above products will make you break out. Currently, I'm using the Josie Maran version in the mornings and the Rodin Olio Lusso (just a few spare drops) in the evenings. Trust me, this is one of the smartest ways to invest in your skin.