I got the device for Christmas in 2008. On that date I added some BIONICLE music and an old Pokémon album. this was pretty much the entirety of my music collection at the time; surprisingly, I didn't like a lot of music then.
During 2009 I added a few video game soundtracks (Cave Story and World of goo specifically). I love both of these soundtracks even today. I enjoyed video game music greatly at the time, but I had no interest in any specific music artists. 2010 wasn't much different, with various video game remix albums added (mostly for Zelda music because Zelda has the best music).
2011 was when my music tastes began to expand greatly. I acquired two albums inn February: Daughtry by Daughtry and Pulse by Pink Floyd. These were the first albums I owned that were not promotional compilations or soundtracks/remixes, and subsequently developed a taste for rock music. For a while I stuck to these two artists, acquiring Leave This Town and Dark Side of the Moon the next month (by Daughtry and Pink Floyd respectively). By April, I took a liking to some other artists, such as Evanescence and Kasabian. I've since grown out of Evanescence since then, but Kasabian remains my favorite band still active, and I now own all of their studio albums. I also expanded my Pink Floyd library with The Division Bell and Animals by June. In August I took a liking to Daft Punk and purchased their live album Alive 2007, which was instrumental in developing my tastes in electronic music. Throughout the year I also collected a number of soundtracks (mostly from Valve, as well as the Okami soundtrack which is still the best thing ever), and some albums from David Gilmour and Cage The Elephant.
Unfortunately the collection ends there, as I replaced my iPod with a new iPod Touch on my birthday in October, but since then my library continues to expand. I still mostly listen to various forms of rock and electronic music, though I've begun to take a liking to other genres such as hip-hop (I currently enjoy Gorillaz and Massive Attack a lot, though I guess the latter is more trip-hop but whatever). I've also expanded my library for many other artists this year, including The Beatles, Billy Joel, The Glitch Mob, Justice, Kraftwerk, M83, The National, Of Monsters and Men, and many more (just naming some favorites).
Yeah, I just wanted to publish this somewhere before I have to go wipe my old iPod. It's been fun looking back and seeing how I've grown.