Sentinel Lighthouse - Best Practice

Hello - 

I've begun the testing and development phase of my Azure/Lighthouse deployment.

Currently: Customer A has defender for endpoint configured.

Goal:
Take defender ATP alerts and centrally manage them in the SOC using Azure lighthouse. I would like to manage the endpoint as well, I believe this is a different technology.

I know I will need to deploy Sentinel for myself and for Customer A

I will also need to deploy Azure Lighthouse to connect to the customer environment.

Which should be done first? ( and ) can this be done in one step?

Notes:
I plan to use this https://github.com/Azure/Azure-Sentinel/tree/master/Tools/Sentinel-All-In-One/MSSPversion

But I don't know where I am in the steps from 
https://docs.microsoft.com/en-us/azure/sentinel/extend-sentinel-across-workspaces-tenants#the-need-to-use-multiple-azure-sentinel-workspaces
to
https://docs.microsoft.com/en-us/azure/lighthouse/how-to/onboard-customer
to
Deploying and Managing Azure Sentinel as Code - Microsoft Tech Community

If someone can give me a 
1()
2()
3() 

Sort of picture in following documentation, advice, etc.
Greatly appreciated!

THANKS!