I won't lie to you, there are some pins that have more value in trading than others. But the truth is a good find is one that appeals to you. There are so many variables about pins that it is hard for a newbie to figure it all out. If you are many in interested in collecting pins for yourself, just look for things you like. When buying pins, sometimes limited edition pins are better
(they have a stamp of LE with the amount of pins made on the back). Pinpics is a good resource for getting info on pins.