From the look of it, your phone is not on the same network. If you do want to use it that way, you may want to look at something like tailscale (mesh VPN). Otherwise, you would have to open it up to the internet which should be considered a security no no in most cases. If you are on the same network, you may need to check firewall rules both network and I don’t know if iPhone has anything on device.
Really the “requirement” is electricity, passed that you’ll need to define “do it all”. I had a desktop with 4 hard drives and 6GB of RAM. Ran containers with Proxmox and it handled most of what I needed (file sharing, Plex, pihole). Then I wanted more, and found an old laptop that has a bad battery and 8GB of RAM1. Installed Proxmox and used containers and ran HomeAssistant and Searx and moved Pihole and Plex to that and turned the Desktop into dedicated storage. Then I wanted more, spent $300 USD on a little mini PC with 32GB of RAM. Now I am running several services (really just for myself) as a mixture of VMs and containers. I still want more, I am hoping to upgrade the RAM in the desktop, and run a backup server directly on my storage.
tldr; you can start with just about anything, but you may always want a bit more