The onramp for finance is accounting. There is no other right answer. This is also essential for general business administration. Accounting is a huge topic; being able to read financial statements is a good, first tangible exercise. Best book I have found for this is Thomas Ittelson, Financial Statements. Using double-entry accounting methods for your own financials with a tool like Beancount is super helpful from a…
Accounting Made Simple: Accounting Explained in 100 Pages or Less by Mike Piper
How to Read a Balance Sheet: The Bottom Line on What You Need to Know about Cash Flow, Assets, Debt, Equity, Profit...and How It all Comes Together by Rick Makoujy
Then I started doing my personal finances on GnuCash, and now on ledger-cli. It's helped a lot both professionally and personally.