The popular VanillaTweaks datapack collection, optimized in plugin form!
This plugin takes all the features all the original Vanilla Tweaks datapacks have and repackages those features inside a plugin for Spigot, Paper, Purpur, and Airplane (and all the other 4000 forks out there) servers.
I highly recommend using Paper over CraftBukkit/Spigot. Paper is a drop in replacement for those and adds numerous features and performance enhancements
Be sure to choose the correct download (Bukkit for Bukkit/Spigot and Paper for Paper + all forks of Paper)
Drop the downloaded jar file into your plugins folder which should be in the root of your server directory.
Startup the server
Open plugins/VanillaTweaks/modules.yml and enable whatever modules you want!
Browse this wiki for information on each modules functionality and feature set