ItemBase is abusing inheritance by using it to run the same code multiple times.
This would work, however it would stop your Item from extending other classes.
You could either do what it does (i.e. setting registry name, adding to modItemList) in your Item's constructor or when you instantiate your item.
I would suggest text-based tutorials. Example being: https://github.com/Cadiboo/Example-Mod
Yes I get it. So was I. Sorry if I made you think I was trying to be a jerk.