Probably the best spigot programming course ever created. super friendly teacher, community overall. everyone there is there to learn and help others. some of the best things about this course is firstly that it includes java classes. so you can enter without any programming skills at all. secondly it teaches you so many concepts that I have never seen in any other course. for example how to make a minigame the right way. thirdly you get unrestricted access to Foundation (a really great API for making plugins quick).
Overall I think this is a really great course and for me it was really worth buying.