The essential oils sold with diffusers are often diluted - These oils are only meant to make a home smell nice.

I purchased my original essential oils at a health and wellness store (the type that sells whey powder and meal replacement mixes), though you can often find them online for lower prices. I know the brand I use isn't the "best," but for adding a little scent to my hair soap and ACV rinse it works great!

There are the two I have:

http://www.amazon.com/Now-Foods-Rosemary-Oil-1-Ounce/dp/B000MGOYZE

http://www.amazon.com/Now-Foods-Lavender-Oil-1-Ounce/dp/B0009RSP38/

I use about 10 drops per cup of water.