You don't have to use the essential oils. You're welcome to skip the essential oils or experiment with other options (lemon, grapefruit, peppermint, etc.).
The oil and vitamin E are added to moisturize the skin. You're welcome to skip these ingredients. Any oil will work: olive oil, avocado oil, skincare oils, etc. The oil won't blend with the water, so you'll need to gently shake the soap before use.
Castile soap is a plant-based soap made from vegetable oils (olive, coconut, palm) and plant oils. There are several reasons why castile soap is awesome…
When you introduce water into a product without a preservative you always run the risk of introducing bacteria, so use water-based products quickly. If you don't have distilled water, use filtered water and use the soap quickly.