There's certainly a lot to learn!
Columns UI with additional plugins is likely the way you wanna go. Your foobar could look marvellous, but you can also choose and pick what kind of functionality you want. Some typical ones might be a panel where you get additional information about the artist you are listening to, a panel displaying the lyrics and/or various vizualisations.
When I started with foobar, I created my own skin from scratch. Sometimes I borrowed code from others, but I always learned what it did and changed it in some way and I had a great time doing all that. It took a lot of time before I had a player I was starting to get happy with though. Now I mostly just tweak other people's skins to my needs.
