If you're looking for some references, Scott Cunningham's "The Complete Book of Incense, Oils & Brews" has a ton of recipes. Anna Riva's "Golden Secrets of Mystic Oils" is a decent reference too. That one doesn't have many recipes if any at all, but it describes different oils and blends and their uses. One of my favorites though is Malcolm Mills' "Potion Book Oils". It has a ton of recipes that can help you understand the components, and through research each one you can slowly learn the properties. I don't know of any essential oil reference books per say, but I'm a google search will lead to many results.
You can start by trying to think of the oils you'll need for the kind of work you're currently doing. Then over time, visiting local shops and/or ordering online, you can start building a small collection of commonly used essential oils and ones you'll need directly for your practices. With a carrier like jojoba or grape seed (the oil I mainly use) you can then start creating your own blends and experimenting with scent, effect, etc. The world of essential oils is vast, but by diving into it you'll also learn about the plants behind the oils.