Unless you are dead set on the use of essential oils, I would look to fragrance oils as a less expensive and more effective method of adding fragrance. It's not very often that I want a single aroma in my soaps. I do however have a variety of fragrance oils I turn to quite often.
My wife's favorite is "Mineral Salt Spa" from Soapalooza; my personal favorite for shaving soap is "Almond Silk" from the same place.
Soapalooza has 1oz "Cheap Thrill Vials" of nearly all their scents for a very fair price. As low as $1.00 in some cases. You could send $20 + shipping and get a whole bunch of scents to try in small batches.
How do they stick?