First you have to choose your flavor. If you want to use JVM, probably clojure. Otherwise Scheme, Common Lisp and Racket. Scheme is rather minimalistic, Common Lisp is very functional and Racket is the most modern one I guess. I ended up with Common Lisp and I rather don't look for change. SBCL is implementation I use and like it. Probably the best one and quite portable.
Emacs seems the best choice for Lisp, since it is scripted in Lisp and it's best adapted to it probably. However when I started, I was already so used to vim that I kept going with it. Maybe not the best option, but it's ok, maybe just a little bit more effort to automatize some stuff.
If you choose Common Lisp, this is probably the best book for start: http://www.gigamonkeys.com/book/ . Anyway be prepared, Lisp is not easy to grasp at first, but as soon you do, you will probably love it and appreciate way it is. :)
just to point out i believe 'functional' here means 'has lots of functionality' not 'more suited to functional programming' - in that regard scheme (and racket) are more 'functional' than CL
Emacs seems the best choice for Lisp, since it is scripted in Lisp and it's best adapted to it probably. However when I started, I was already so used to vim that I kept going with it. Maybe not the best option, but it's ok, maybe just a little bit more effort to automatize some stuff.
If you choose Common Lisp, this is probably the best book for start: http://www.gigamonkeys.com/book/ . Anyway be prepared, Lisp is not easy to grasp at first, but as soon you do, you will probably love it and appreciate way it is. :)