Question as an aspiring web developer with a moderate-high degree of comfort in Javascript, and low-moderate comfort in Ruby: would you recommend giving 100% to mastering Rails, or dabbling with Meteor from time to time?
The aim is to not get a job as a developer, but build my own projects.
Apologies if this kind of question is better suited for Stackoverflow
For side small side projects, where you want start and move quickly - I totally recommend Meteor. Before knowing _any_ framework I started reading on Meteor - and literally in hours, I had a simple app.
(Actually, it's how I use it. I am mainly data scientist; I do some webdev, but its not my main thing.)
As a side note, one of things that made me using Meteor.js is the easiness of starting (largely to great official examples and tutorials).
BTW: I highly recommend Discover Meteor by Sacha Greif & Tom Coleman (https://www.discovermeteor.com/). One of the best tutorial books I went through.