Deployment does require a specific order
perform terraform init/plan/apply in these directories
(any of the following three in any order)
You then have a choice of transit-gateway or VPC peering
You may test both, just make sure you destroy one before deploying the other
global/prod/main/vpc-peering
global/prod/main/transit-gateway-peering
You may optionally deploy EC2 instances for testing
Make sure to change the key_pair to an appropriate value
Cleanup is "terraform destroy" in the reverse directory order of deployment