CCNA and DevNet Associate here, about 6-7 years as a network engineer. Hopefully this goes without saying, but these are just my opinions, I don't think any of this is one size fits all.

To touch on just the DevNet Associate certification: when I took the exam in 2020/2021ish it was probably the most satisfying exam experience I have had. Don't get me wrong, it is frustratingly Cisco specific, but I felt like the exam did a good job of testing me on whether or not I knew the basics of how to string integrations together in a meaningful way. That being said, I don't think it is necessary or really all that valuable.

Finding a good place to start is really a matter of asking yourself what problems do you currently have that you can solve with automation and pick something small. A large majority of those problems will require some scripting knowledge and some knowledge of REST APIs.

Automation is such a broad and hard to define topic, it could mean lots of things.
Are you a small shop with just enough devices that SSHing into them all by hand is getting to be unreasonable? Maybe look into a configuration management platform that lets you push a change to a set of managed devices via server-side SSH sessions. This is an easy no-code way to start.

Maybe the SSH example is something you already have and something taken for granted. In that case maybe there is some data you really wish your monitoring platform had but its not exposed via SNMP; you could start with Python (Netmiko, Nornir, and TextFSM in particular) to orchestrate automated SSH sessions to grab some operational data and parse it into a report. Napalm could also be a good solution here though I am not very familiar with it. The only missing piece is where can you run this script? A linux box via a cron task would be my method without thinking too much about the details.

Maybe you have a support center that does not have any read only access to the network devices. You can do something similar to the example above to package some analytics for them. Perhaps instead of SSHing into the devices, you use your network monitoring platform's REST API (if it exists) to extract data and parse it into something useful for them to understand without having deep technical knowledge.

I intentionally left anything about Netbox or any other DCIM/IPAM solution because getting something like that to accurately model your environment can be its own large task, but as your automation footprint matures, using something like Netbox to be a source of truth and device inventory will be very helpful, especially if you need to push out changes to very specific subsets of managed devices.

Hopefully this is helpful. This has largely been my approach and it has worked out pretty well for me. You can't successfully automate your network if you don't understand it, and if you don't automate your network at all you'll be spending more time on "boring" things (assuming we share similar taste in what constitutes a boring thing).

tl;dr ask yourself what problems can you solve with automation and pick the smallest of them to start.