I think the "understands the language and ecosystem better" is critical, but my expectation is that I need to learn a subset of key gems better more than anything else.

Every hardcore Ruby-ist that I've known has owned a Mac as their primary dev machine. I'm sure that there are plenty of Linux devs out there, but my experience has been that it's heavily Mac-driven. However, by sticking with Linux as my development platform, I'm probably going to learn the guts of gems because I have to get under the hood to make them work on Linux.

Maybe I'll continue to have gem conflicts, but that's okay - I'll know how to hack around them.