What are the important KPI's to be on the dashboard of ERP?

An ERP is a combination of different business areas / Modules. Hence for aquiring the desired knowledge first you need to identify the Business Area.

Typically as an example, I can tell you that if you see the financial module then there are different sub areas which are as follows :

General Ledger, Payables, Profitability, Receivables etc.

Now if you look for Manufacturing Area, following are the sub areas :

Inventory, Production Costs, Production Performance, Production Plans etc.

Now if you see the Supply Chain and Order Management Analytics, Inventory is also the part of it.

Hence you need to identify your learning goals first and then you can find the desired information.

Hope the above mentioned information will  help you to move in the right direction.

Good Luck!!!