I bought most of my starter flavors from the perfumers apprentice. They try to make most of their flavors water soluble. I have read that using oil based flavors can be difficult, so I stick with the water soluble ones. I also try to stick with clear flavorings as it is really unknown how the colored ones can affect an individual or your e-cig set-up. I have been diy for almost 2 years, and i do try different things on occasion, but i usually stick to my 2 rules listed above.
Good luck!