That was how I started collecting, casually in 2002, seriously in 2003. I was advised by my fellow traders as to which characters currently were the most popular and (well-intentioned) cast members suggested that I purchase every limited edition pin I could acquire, in multiples (one for my collection and extras to trade). Needless to say, I started off on a mission to acquire every limited edition piece of shiny metal with a pointy back attached to it, in multiples, never mind how I actually felt about the pin itself. I figured, hey, even if I don't like it ... it's limited edition and a good trader; someone will like it, right?
If I had it to do over, I wish that someone had told me NOT to do exactly what I did, but to select a character or theme (or maybe a few, depending upon how prevalent the chosen character/theme is to acquire). If you aren't careful, it gets too out of control and you'll end up with too many pins and no place to put them (this is personal experience talking). I've since narrowed down my collection to my primary with a few narrowly defined side collections and I can't remember the last time I acquired a pin that didn't fit into one of those collections. I'm currently now devoting as much time as I can spare to sorting through boxes (no exaggeration) of pins; I need to figure out what exactly I've got and list it for trade or sale.