Reply to Expanding your DJ library for a newbie

Im new to djing and just got myself a s2,amp and speakers I have a ok collection of music but have realised that I need a lot more music from many different genres and need to expand my collection.So im just looking for some advice on whats best.I have mostly been buying from amazon but am wondering if there is better ways than just buying albums or individual songs.Ive heard rhapsody is good ,they have a monthly subscription but i dont no if you can download music as part of the subscription.
Any advice info?Where do the seasoned pro's get there collections from or is it just a process and part of becoming a dj to build your own collection?