Are you trying to install on shared hosting? You don't need to do all that. The readme has the link to the tarball that has everything already in it. All you will need to do it upload it.
If you're cloning, you need to run `composer install` in order to get all of the dependencies and stuff. I'll update the wiki page to remove all those instructions. The error 500 could be because you haven't done that. It's impossible to know without looking at your server's error logs, which is where I would start if I were you