DBA's - What did you do that helped you gain the most understanding in your role?
If you're referring to Microsoft SQL Server then my path directly applies, otherwise you can derive the same generalizations and apply them to the database system you're learning about. The following four things were the major contributors to how I grew in my DBA knowledge:

Brent Ozar - Specifically I was lucky enough to stumble on his podcast Office Hours and would listen to all the old ones everyday until I was caught up and then I'd participate in asking questions in the new live sessions. (You can find the podcast on any modern podcast system.) This helped introduce new key terms and system features in my brain, even if I didn't fully understand them at the time. Just hearing the vocabulary used over and over was super helpful in itself.


RTM (Reading The Manual) - After I got hooked on Brent Ozar, and learned a lot of new key terms, I'd read the Microsoft documentation a few times over on that feature to try to understand its purpose and how it's used. Some days I'd scan page after page in the documentation looking for more features I wasn't aware of. I was hungry to have at least heard of every feature SQL Server had to offer.

Reputable Articles and Blogs - Aside from all the content on Brent Ozar's website, there's a ton of reputable sites out there with awesome information on everything SQL Server under the sun. To name just a few of the many, SQLPerformance, RedGate's Simple Talk, Erik Darling Data, Kendra Little, Pinal Dave's SQL Authority, anything written by Aaron Bertrand on the multitude of places he contributes to (including SQLPerformance), among many many others out there. I initially stumbled on a lot of these from Googling issues I ran into with SQL Server as they came up, or when trying to further my knowledge from the Microsoft docs.

DBA.StackExchange - This site has always been greatly helpful for me, especially when I was in my early phases of learning and got stuck. I learned a lot from the many questions I asked on here, and resultantly continue to further my expertise as I share that knowledge to help others on here or as I am forced to research more into the answers I provide to others.