Reddit mentions of The Bloomberg Way: A Guide for Journalists

The Columbia Guide to Writing About Business is a solid intro to business ideas and coverage, if a bit dated. The Bloomberg style guide has a ton of information on what to look at specifically on certain financial beats. It references its own terminal a lot in looking up data, but most of that can be found searching yourself. Marketplace's daily radio show is very US-centric, but it does a good job of explaining complex global topics at a layman's perspective.

And some advice from me: I studied political science in school hoping to cover statehouses and campaigns and got thrown onto the business beat by coincidence. Always remember governments can make a big difference in how businesses operate because they set policy and they're often massive consumers themselves. And always remember that no one person or entity acts independently in an economy. Everything from financial reports to board changes to politics and weather events in one part of the world can have big ramifications from what happens to a business on the other side of the planet.

Good luck! PM me if you have more questions and I'll try to answer best I can.

EDIT: Forgot about the Reynolds Guide to Business Journalism. It's free but a lot of the beats are focused on a western audience. You might find the economics and the energy chapters particularly useful.