Essentials? Difficult to decide, it depends on why you are even selfhosting in the first place.

At a first glance and looking at my attempt at a homelab:

• some sort of basic web service (eg.: nginx + PHP setup)
• some sort of repo manager service (I do Fossil, but I hear most people use eg.: Gitea)
• XMPP server
• Jellyfin server
• Minetest server