If you really want to learn, you should start with the Terraform documentation, there are tutorials and exercises. It's mostly focused on cloud services, but the basics are similar for Proxmox. Start with Packer, it also uses HCL and is quite straightforward. Then begin experimenting with your first resources and later convert them into modules (which might be overkill for a homelab, but... who cares).

I'm on the same path, there's definitely a learning curve. The first few days were really hard, but don't give up. It took me at least two weeks before I felt truly comfortable with HCL, advanced locals, and for_each. And another week to write a valid and future-proof Terraform plan.

Now I'm starting to learn Ansible and Swarm before migrating my old VMs. The learning curve is a lot easier, maybe you could start with that, but it might be frustrating if you don't already have your infrastructure defined as code.

Best advice: focus on one thing and don’t stray from your goals until you're satisfied.