So i have just swapped over to mac from ubuntu and setting up the env has not been as easy as promised.
this is the process i followed.
The problem seems to be that you're using a system ruby installed bundler, and not one installed with your rbenv ruby.
Run ruby --version
to make sure your rbenv ruby is active, then run gem install bundler
followed by rbenv rehash
and then try reinstalling your gems and see if that works.
After many installs of rbenv, I too was unsure of why the correct ruby was not being used. Turns out the insertion of the eval statement was prior to the reorganized exports of PATH and the eval failed quietly. Make certain the PATH is established above the eval statement.