Run the datagen task before doing anything, and then you can either build or run client after that
If for some reason you can't get neptunelib, go here and make sure to press GET IT on the latest release, that should build the latest release on jitpack, which is a fallback for builds.
Any actual members of Neptune Development must go through the other method.
To be able to build the project, you'll need to set up some things manually in your global gradle.properties
This is a global gradle.properties file, you'll need to find your .gradle folder, for Windows it's in your user directory by default (The folder before AppData)
If you don't already have a gradle.properties file there, then create one
You'll need a personal access token and your username for this next step
gpr.user = USERNAME
gpr.key = PERSONAL_ACCESS_TOKEN
Just make sure reload your gradle after that
This isn't really required, but if some reason you need to test an experimental version of neptunelib, this is the fastest way to test it.