I'm a bit of an outlier when it comes to essential oil use. Generally, I just slather them on, or ingest them directly with no problem. Now, you've got to be super careful with some of the cinnamons. Earlier this week, I was filling some small 1.4 mL vials, and I had a gentlemanly itch. Needless to say, I now had Cassia oil in a very tender spot. A shower quickly ensued.
As for the oils, I don't plan to dilute them at all. I've got my tick oil mixture that is going to go probably on my skin by my ankles, but maybe just on my socks and my pants cuffs. With these oils, the carrier is the other oils that might not be as effective of a repellent. So, while I could have an effective concentration of one ingredient, I would rather have a blend of many.