When changing into Rails folder, have rvm pick ruby and gemset?

For current versions of RVM, using two files is best practice:

.ruby-version
.ruby-gemset

http://rvm.io/workflow/projects

Create a .rvmrc file in your rails directory, and rvm will automatically load it. An example .rvmrc that loads Ruby 1.9.2 and a gemset named "rails3":

.rvmrc

rvm 1.9.2@rails3

You can do a lot more too, described in detail here: https://rvm.io/workflow/rvmrc/

You can also use this in Gemfile

ruby '2.2.0'
ruby-gemset=significa

This way rvm will automatically pick the configured version