[sbt]

I had the same issues starting CL. I think which LISP you pick is less important in the long run, rather than getting into the mode of writing functional programs. At some level, writing CL and writing Erlang are not that different experiences, to me at least. I know this sounds like abstract advice, but this is going to be a long journey anyway, so the most important thing is just to start it. Get Graham's ANSI Common Lisp book, get SLIME going and write something self-contained, like a basic matrix library. Worry about libraries later.