Looking to become more knowledgeable in GRC - best approach for someone mid-career?

I'm looking to improve my skills and knowledge around GRC. I've already got a full-time job as a security engineer but I'm starting to do a lot more GRC stuff for the company.

I helped out with gathering evidence for our PCI DSS RoC Level 1 which was incredibly grueling. It made me realise I don't know shit about GRC lmao.

Also, I do not have a training budget so would appreciate any free or affordable training options.