How can i build a more diverse music library?

Well I'd start with the typical 'gateway' [as one of my contacts calls it] artists/bands first.

When people are getting into Classic Rock, they often start with Led Zeppelin.
Then start to search for similar artists within the same genre.
http://allmusic.com is excellent for that. You simply type in a band and they provide several similar bands, and influences to that particular band/artist. It's a great way of finding new music.

If you use wikipedia, and type in a particular musical genre then a lot of the time, they'll mention some of the most celebrated bands/artists from that genre. For example Celtic Rock; http://en.wikipedia.org/wiki/Celtic_rock... They mention quite a few bands including Horslips and Clannad.

To ensure that you enjoy the type of music, use Youtube to sample some of the music first. http://youtube.com
Once you've found a prototypical band, enter it into Youtube, if you like it - purchase one of their albums.

Once you've done that you can start to branch out and find the variations of different types of music.
Yahoo!Answer's music sections are great places to get recommendations on particular genres and subgenres. There are always people willing to help.

get different types of music...?

http://www.emusic.com

start with genres and branch out. For instance pick a type of music..... Rock and than the artist..........Ac/Dc, Aerosmith, PinkFloyd so on so on