Lets start out with the essentials on every public server.
- A PLUGIN EXPERT, If you don't know what to do then you need to have a pro help out!
- PermissionsEX (Permissions), Requires Modifyworld
- HeroChat (Chat Formatting)
- Prism (Block Logging and Rollback), Requires MySQL
- MCBans
- WorldEdit
- WorldGuard
- CommandBook (Basically Essentials but a lot better)
- Vault (API for alot of plugins)
- ProtocolLIB (Also an API)
Then there are some "Optional / Required ones" These plugins are required on some servers, but may cause problems on other servers.
- CraftBook
- LWC
- Multiverse (Core, Portals, Nether Portals, (Inventories))
- OpenInv
- PlayerData
- PluginReloader (Recommended for large servers)
- VanishNoPacket (A Vanish Plugin)
Those are my recommended required mods, There are more you can use but i believe those are required.