I am not aware of any vendors that give away free samples without a purchase. But, there are many vendors that sell very reasonably priced sample packs (usually in small 6ml bottles).
As someone that has purchased hundreds of dollars of ejuice duds over the years... I highly recommend buying samples first.
That, or I would google B&M's and be willing to drive maybe an hour out of your area to sit down at a
juice bar. It will save you money and you will be much happier in the long run.