why don't you install gem via your package manager?
deken is mainly for people who cannot afford a decent systemwide
software management system.

Would you recommended to to install externals by default package manager such as apt-get or pacman? I'm not sure, but I thought the some packages on default Ubuntu(14.04) server is a little old or outdated, but pd-deken is an up-to-date-system for missing packages, and I'd prefer pd-deken over apt-get. Please tell me if I am wrong.

best,
jonghyun