It's only as safe as you make it, and improving your sysadmin/security/devops skills is a requirement that never goes away imo.

It's perfectly fine to try it with something you don't care that much about for starters, a baikal calendar is a nice and easy start. Expose only the ports you need for your reverse proxy (and also ssh if you don't plan having the machine in your local network), and the rest should be secure enough for just small services for your own and your family's usage.

Eventually you will start learning how to backup your data with cronjobs, strengthening security a bit more, and as you go you can keep adding increasingly important services for yourself as the system becomes more reliable.

Edit: Hardware is very expensive now, but if you have an old laptop that is just sitting collecting dust, it's the perfect starting point for a server. It's not ideal long term, but it's a free way to get your feet wet and learn.