Why can’t you fix rate for your product? You deserve for it as it is your hard earned produce.
Harvest Mangos after 75% ripening in tree itself, subject to thefts.
Allow them to ripe naturally without any application for ripening.
Mangos should be harvest without any damages with special equipment Allow mangos to dry for some time.
Start giving few mangos as complementary to your neighbors/colleges or any others near you.
Explain them as how you grown these mangos,
Let them taste and come back with further more demands with even comments about taste, variety etc.
Than you fix rate close to prevailing market rate and gradually increase after getting permanent customers.
Gather carton boxes, some customers may order you in bulk with decent package for transportation.
Fix your own price and sell. Initially it may difficult, but later it will give you pleasure.
Have nice marketing.
Come back with experiment and result.