Madvapes (top vapor USA e-liquid link on left side) has a good selection of inexpensive, simple flavors. Candy cane, tuitti fruiti, cotton candy, fruit, citrus, and candy flavors. The licorice is good, but not real sweet. Same goes for the blueberry. I haven't tried too many of their flavors, but most of the ones I've tried are good. I had high hopes for fireball, which smells like good cinnamon, but tastes aweful. They don't have samples per say, but, you can buy a 5ml bottle in a number of different strengths for very cheap ($2.29 each at 18mg/ml), shipping is fast and cheap too. They do have some packs, currently they are running a sweet tooth pack, 10ml each of five different sweet flavors for $14.99 in 18mg/ml. Of course you could select any five flavors you want in the same size and strength for $19.95 at the regular price ($3.99 each).
Their flavors aren't as strong as they could be, and they don't flavor boost. But they do sell flavor concentrates, but not in all of their flavors (I don't think), so you could boost them yourself. The flavor concentrates are inexpensive, and I'd still recommend their ejuice. It's inexpensive enough that you can try a few and not be out much even if you don't like them.
