as EPCOTgirl said the cast members have to trade with you
but there is this pin station in the middle of Epcot and you can buy pins there or you can trade or both but ther e are alot of ppl that do have alot of pins but you might be able to find someone more at your level and trade with them but remember if they're not cast members they dont have to trade.
also my mom and i got in to trading like 4 years ago and my mom found groups of ppl that also trade dis pins that live near us and we set up a place to trade and get to know each other and we traded pins online with ppl also and when we went to
Disneyland CA there was a meeting for ppl to trade and my mom and I went there it wsnt all that good though but there is alot of different ways to trade
you can have a lanyard, abook, or a vest of pins (those are just ways to carry them around depending on how many pins you have)and you dont have to trade your pins you can just buy the ones that you like and collect them or you can collect them and get dupicates so you can trade those for other ones
and some times if there is a speical event there are spiecal pins like for the Very Merry Christmas Partyand when i was in California i went on a pin scavenger hunt almost and i got glow-in-the-dark pins they were speical edition they dont sell them and they dont make them anymore
i hope i helped you have fun trading