I mostly work with an offline digital connection. It's so much more convenient that constantly searching for and swapping physical media.
For full albums, I tend to buy them on CD, and rip them to lossless audio. I then convert to lower bitrate lossy audio when exporting to my phone for listening when I'm out and about.
For individual tracks, I'll buy them as digital downloads for the convenience.
I find YouTube is great for finding new music, but when I find something that I like, I'll usually end up buying it.