I make mine in loaves. Each loaf is 13 bars. So, I'd probably offer mine by the loaf.
It depends too, on how much space they have to sell your product and how many kinds they're buying.
You want them to be successful with it so they'll buy more, so maybe make up an assortment of 4 bars of each of 6 kinds or something... Then, they can see how it goes without investing too much, but still have an attractive variety to display.