Definitely FlavourArt for tobacco flavorings, but in my experience:
Flavoring concentration can be a problem to develop-- it's a very individual thing: some people will like 2%, others prefer 12%, most are somewhere in between. And it varies between different flavors. And up to a point it also varies with aging time.
Tobacco flavored liquids seem to require the most aging until the full flavor develops, especially if two or more flavors are combined. It can be shortened somewhat by periodic heating and shaking, but think in terms of weeks if you're serious about obtaining the best possible taste that is stable over time.
I'm not trying to discourage you Jeff, but in starting out I've made a lot of attempts that ended up in the "Tobacco" bottle. That was not a money saver at all. It's possible to make good low-cost juice, but only after you've discovered that which suits your personal taste.
I would recommend starting gradually, with a single flavor, making small, 2-4mL sized carefully-measured batches and writing down the recipes for each. Use 6mL bottles*, label each with something like "Cuban 6% Dec.11" which you can track back to your notebook. Give each batch at least a week before sampling. Write down tasting notes.
Try making a group of samples in the same mixing session with a spread of percentages such as 4% - 6% - 8% and compare them with each other after they've aged a bit. If you like the 6% best, then the next group could be 5% - 6% - 7%. Save some of the samples and compare them again after a month or more has passed; you may be pleasantly surprised at how they've changed.
Don't expect to completely switch over to DIY juice right away, so continue to order your regular premixed juice so that you don't run out of good vape, at least until you're confident that you can reproduce tasty recipes.
*nearly as cheap as 3mL but easier to add liquid, harder to tip over, has a larger area for label, plenty of headspace for shaking