How do you get this to work?

How do you earn $ to upgrade each skill? I have economics and server rewards installed but nothing happens when I gather, loot or kill?

Skills plugin allows you to buy skills with $ (or any other currency), but it doesn't know how to accrue this currency. You need to install a plugin with which your players will get $, for example:

https://umod.org/plugins/gather-rewards

https://umod.org/plugins/play-time-rewards