If i may jump in here,
Did somebody succeed with Gem+Pd048 on Mac ?
Yes. Are you are using 32 or 64 bit pd and which version of Gem did you download?
I saw an article about adding "libdir" library before Gem, but it doesn't work for me.
-lib Gem is enough
I prefer putting a [declare -lib Gem] in the patch instead of loading it on startup. But it depends on what you are doing.
Cheers!
fd