There is a company called Primavera that sells a lot of great base and essential oils, mostly organic. http://www.amazon.com/Primavera
Including an organic avocado oil. Avocado is great, but you might also want to look into Pomegranate and Shallow Thorn Oil (Sea Buckthorn), those are great as well. Squalane is also very good.
Also, do you use oil as a cleanser? It’s a great method for cleansing the skin without stripping its natural oils or harming the skin barrier as foaming and detergent-based cleansers do. If you use a natural soap directly, its PH is too high for the skin which is slightly acidic, and detergent cleansers harm the skin barrier/protective mantle. Most people using the oil like a mix of olive oil and castor oil. Massaged in and then using a wash cloth drenched in hot water you steam your face for a minute and gently wipe it off with the cloth. Other oils can be used too like Hazelnut or Camelia. Apple Cider Vinegar makes a great toner afterwards, even mixed with a green tea or Rooibos tea. Witch Hazel is also good. Wine or Sake make good toners too. I don’t think you need expensive or fancy skin care products, but there are some good ones. Making your own stuff though means fresh and no preservatives or additives. A lot of people like Dr. Hauschka’s cleansing cream, but I’ve seen a homemade recipe for it as well. It’s just basically almond meal and oils and witch hazel. It’s less expensive to make yourself. Works great as a gentle exfoliant and cleanser. You can also make your own body exfoliant in 2 seconds by mixing sugar and olive oil, with maybe some lemon juice or some wine.
Eating vitamin C rich foods is great for the body and for anti-oxidant protection, but it’s of little benefit for increasing collagen levels in the skin because you can’t obtain high enough concentrations of vitamin C in the skin by ingesting it.