I'd say start with getting Lemmy going inside your home network (not accessible to the outside world). That'll give you a chance to play around with Docker if you want to go the Docker route. I like to make Portainer the first docker container I install (I install it with Docker Compose), and then I manage all other docker containers/etc. through Portainer. Just a quick heads up on Portainer... what Docker calls "docker compose", Portainer calls a "Stack", because it can have a "stack" of different stuff running under it.

Anyway, from there I'd figure out a reverse proxy. I use Nginx Proxy Manager, which is nginx under the hood, with a web interface to manage things. I've never tried Caddy, but people like that one, too.

The reverse proxy is what controls security, basically. Someone from outside your network types in lemmy.superspruce.org, and you've told Dynadot to forward that to your home IP address. You open port 80 and 443 on your router, and forward them to the machine running Nginx-Proxy-Manager. So NPM gets everything that's pointed at your house on those ports. It see's the request is for lemmy.superspruce.org, and you've told NPM where to look for that, and it handles it from there.

Just doing these things will open up all sorts of learning challenges that you'll have to figure out through Googling.

It took me years to finally decide to figure out a reverse proxy, and once I wrapped my head around it it makes so much sense. I wish I had learned it sooner.