The value of your pins, more or likely, is what they mean to you. I haven't actually seen a book that tells you this pin is worth this, etc. Most people put a value on their pins but either the event or the meaning behind it. Think about what you like. For example, I wanted to collect them all

... yeah, not practical. So I traded and collected by favorite characters, like Belle, Tinker Bell, Pixar characters. From time to time there is a set that I just "love" and I have to trade or buy to have them all. "Help I am addicted to shopping for pins on ebay"....you get the point.
I know that I always bought a pin from the Yacht Club every time I stayed there. For me, it represented the resort I enjoy and the pin represented the year I went the on vacation.
There are no rules to pin collecting. And since you are just beginning, you can start your collection any way you want. Look at some of the links listed above and just see what you like. But be careful, before you know it you will have hundreds of pins and you can't figure out how that happened

and forget about trying to calculate the money you have spent; it will scare you

.
Have fun and welcome to the pin trading world.