This has been intended to be a simple way to talk to nrepl from Vim. I've almost succeed - the only excess here is nREPL sessions support, but it is important - it enables ClojureScript support. See plugin docs for details.
I would recommend Pathogen to manage your plugins. With Pathogen installation looks like:
cd ~/.vim/bundle github clone https://github.com/shashurup/vim-gains-nrepl.git
That is it. You also need Vim => 7.4 with Python support to use this.