Usually, I'll end up buying the whole album if I end up splurging and actually buying the music. It's because I've been anticipating the album of the group coming out for awhile and want to have the whole thing. The most recent group I bought, the Dirty Loops CD, was one I waited to get since I heard them on youtube the first time. For most of my music though, the prime version of Spotify and Youtube fills 95% of my music listening need.
When cassette tapes and cd's were popular, I buy the album of the artists that I like, since I know there's a good chance that I will like most of their music in their album. But now that you can easily download songs via the net, I just download both songs and full albums for free.
I but the whole album, because first, it's cheaper per song when you buy the whole album than buying each. Second, when I listen to a song, often I will also like to listen to the songs that it came along with when it was released. Third, album is an art where arrangements of the song, which follows which and which precedes which, give me another insight to the songs that I am listening and to the artists themselves. The whole is more than the sum of its parts, this is how I justify my impulse on buying albums, instead of just one of them.
Honestly i can't remember the last time i bought a song/album. It's just so easy for anyone now to download songs online for free so i take advantage of that. I know it's not legit but everybody does it so i don't feel so but about it. But if you really want to support the artist, sure you should just buy their music.