You don't need much at all if you're asking hardware-wise. Depends on what you want to host but I run jellyfin, searxng, slskd and many other containers on a small Intel CPU and 16 GB of ram. I run all of my containers in docker-compose and have no issues. Storage wise, all of my containers run from a 1 tb ssd, the containers themselves only store your config files, etc so you don't need much storage for that. If you wanted to run like Jellyfin for media then you would probably want more storage.