The third major way you should be conservative with your oils is diffusing (actually it’s quite possibly the first).
If you don’t read any farther in this post, read this: whatever you diffuse you will use up fastest. Case in point, I just got RC last month but had to diffuse it nightly for respiratory support for Madeline’s and it is now empty. I diffuse thieves daily for immunity and go through it like crazy. Thankfully neither of these are terribly pricey though.
My first major mistake as a new EO user was being captivated and overly excited about my diffuser. I couldn’t wait to brew all different amazing smells and to play with my new toy. I looked up recipes for different combinations. Mistake.
Again, be wary of Pinterest. Some of the recipes would tell me to use 8-10 drops of each EO! That is just crazy! And expensive. For a smaller home like ours, you only need 4 drops or so TOTAL to get the effect you’re after for your diffuser. So if I’m diffusing purification and thieves, I’m using two drops of each.
A final tip I’ll leave you with on diffusing is to think of oils you don’t use much. One I diffuse often now is citrus fresh. I love the smell, it’s uplifting, and I don’t need it for other uses so I don’t feel like I’m wasting it when I diffuse.