Other than the primary tutorial video series, many of these videos are outdated, and remain here as a historical reference.
The primary video series starts at "Setting Up A Local Test Server and Your First Task Script" and ends at "Putting It Together: NPC Guides", with videos in order, labeled from 1 to 28.
All videos outside that series should be considered very outdated and historical.
Videos 
within that series are somewhat outdated but still somewhat valid and perfectly acceptable to use in year 2019.
For details on what has changed since this, refer to the 
Updates Since The Videos page of the Beginner's Guide.
Please join us on 
Discord and/or view the in-progress text-based 
Beginner's Guide