I am staring to sell bamboo plant arrangements and this is the first time that I am doing any kind of business?

figure out how much each arrangement costs you. if you have $50 worth of bamboo and you plan on selling 10 arrangements that would mean you have $5 worth of bamboo in each arrangement. do that with all the supplies. then factor in how much time and effort it takes for you to make them and how much you think you deserve and add that to the price

ex:

$5 bamboo

$5 for each vase or whatever the heck you put them in

$3 some other decorative item(s)

$10 for your time

= $23 each arrangement

another thing you might want to factor in is stuff like gas or shipping supplies

Check for competitors and follow their lead.