I started collecting last Oct, about halfway through my ten day trip. So, I didn't do much trading, but I did end up spending about $500,

on pins. (And then I wonder where all my money went.

) After getting home I discovered Pin Pics, (you can view my collection there - disneyfav4ever as well as my wants and trades.) Also, I've bought dozens of pins off of E-Bay, which is my main way of collecting now.
I agree with what a previous poster said, most of the cast lanyards are filled with Sedesema and Pro Pins later in the day, and while I collect the pins I like, and don't care about the actual money value, I do want just "official" Disney pins. I did, at WDW buy a few starter sets for around $5 a pin, but they were official, so I didn't feel bad trading them away.
For my next trip, in Dec, I plan to buy a lot of official pins off of E-Bay, to use as traders. I may take a few from my collection, that I don't feel are "must-haves," but for the most part, my collection will stay home, where it is safe.
As far as buying in the parks go, I probably won't buy many, if any. Who am I kidding, even if I say I'm not going to buy any, that'll probably only last a day.

But, I'll try and limit myself to LE's, like the ones from the
MVMCP's I go to, and special Christmas ones and such.
For the most part I've been limiting myself to princess and animal pins, though I just can't resist some other ones, like the postage stamp pins, art of celebration, friendship, and romance. I started collecting, thinking I was just going to go after Jasmine and cat pins. But then there was an adorable Lady, and a pretty Belle one, so that lasted about five seconds.
Some of my favorites are - Scar, from the Disney masks collection, Simba from the 2004 Flower and Garden Festival, which is a LE of 2500, the princess pairs and icons collections, the Jasmine original dress from DLP, as well as the one with her and Ali dancing, also from DLP. Some of my favorite pins where only available from Disney Auctions, there's one of Marie, from the Aristocats that is an LE of 250, a winter flurries Belle, that is a LE of 250, and one of Belle and the Beast with the rose, which is a LE of 500.
When I trade, I look for any pin I like, regardless of if it's a Cast Lanyard exclusive or not, though I do really like the new Chip and Dale series with the Disney desserts.