Nisad

Congrats on the new role! A month is actually solid prep time. Here's what I'd focus on:
Ruby first, Rails second. If your Ruby fundamentals are shaky, Rails will feel like magic you can't control. Go through The Well-Grounded Rubyist or just grind exercism.io/tracks/ruby for a week.
Then Rails: the official guides (guides.rubyonrails.org) are genuinely great — don't skip them. Focus on ActiveRecord, routing, and the request/response cycle.
For intermediate/advanced: look into service objects, concerns, background jobs (Sidekiq), and how to keep fat models slim. The Rails AntiPatterns book is old but gold.
Testing — learn RSpec basics. Most serious Rails shops live and die by it.
Good luck, you'll hit the ground running!