For --path, I just use the default which presumably puts everything in the main rbenv folder for gems. I've never had a problem with this.
For the problem of having to type "bundle exec" before every command that uses a binary from a gem, I've heard of two alternative solutions. One is aliasing "bundle exec" to "be" or something to make it quicker to type. The other is using zsh/oh-my-zsh instead of bash and using a plugin (can't remember the name off the top of my head) that automatically figures out what should be bundle execed and takes care of it behind the scenes. I've never had trouble with this either.