It would be good if you could post some images here, especially of any that you think are more scarce.
I do collect FDCs from this era, but I am not an expert on this issue. If there are 14 different cachets, then some will probably be more scarce. Their value will depend on condition, scarcity and demand. It is difficult to guess a price without some sold examples to base it on.
You can check
ebay sold listings to see if any that you have were sold, and at what price.