Not all essential oils can be used directly on your skin.. as a matter of fact… i can think of only one off hand that is completely safe full strength and that is patchouli.
As for doing it as a business, it depends where you live as to what regulations you will have. I would have to get an ‘alcohol license’ here in Norway if I wanted to start using alcohol in the products I make at home because I’d have to import the special ‘perfumers alcohol’.
Making solid perfumes where you suspend the fragrance in a moisturising base would be a bit easier.
Check out Etsy for ideas, but chemically it’s pretty basic. Alcohol, fragrance or essential oils, and something to get them to mix like a polysorbate.