The problem with an EO spritzer is the that essential oil will NOT dissolve in water. What you will need is to first dissolve the essential oil in a solublizer...either VERY high proof vodka, Everclear, or Perfumer's alcohol if you have access to it, or a substance called Polysorbate 20.
Mix the essential oil into twice as much of your chosen solublizer, then add distilled water.
Now...the amount of oil will depend on the proposed use:
For 4 ounces of distilled water use:
8 to 10 drops for the face
30 to 50 drops for an all over body spritzer
80 to 100 drops for a room spray/air freshener