@riley I would also like to add that the CL community is relatively small, but it does have passion and is very much alive. We have even had increased activity with the introduction of online meetings where we showcase projects. The community is mostly focused around #lisp #lispcafe #clschool on freenode (they're also accessible via the matrix bridge). The online meetings can be found here https://www.youtube.com/channel/UCymtXMj1M7cKiV9TKLoTtEg/videos
Most beginners are pointed towards http://www.gigamonkeys.com/book/ but it is also worth just diving in and asking questions while referencing this to find out how to do '''trivial''' (for lack of a better word) things.
The editor I recommend using is https://portacle.github.io/ to begin with, however this comes with a structural editing mode called Paredit, which can be very confusing to a beginner, basically you manipulate the lists with the keyboard rather than deleting and unbalancing parens. There is a cheat sheet here https://github.com/georgek/paredit-cheatsheet/blob/master/paredit-cheatsheet-refcard.pdf
If that is too much you it can be disabled and you could use alternative editors (Vim, Atom and Sublime now all have extensions supporting interaction but I do not recommend them, I would strongly recommend attempting to use Emacs (Portacle) + Paredit first)
@vertigo With quicklisp (and the quicklisp distribution) all the systems are built against each other each month and are all compatible with one another within one release. Most systems and their protocols stay the same so it's seen as much less of a priority by the community to solve this problem (granted it's not sustainable but this at the moment for the large part it isn't an issue)
There is qlot https://github.com/fukamachi/qlot if you need to freeze dependencies or pull in things that aren't in quicklisp. Although I haven't needed to use this myself
If you need help with anything else I would recommend asking questions in #lisp or #clschool on freenode, they're sure to get an answer to you quicker