you can find all the limitations related to NSX-T in this link
https://configmax.esp.vmware.com/guest?vmwareproduct=VMware%20NSX&release=NSX-T%20Data%20Center%203.2.2&categories=17-0,18-37,18-46,18-32,18-33
according to the table
Tier-1 Gateways per Tier-0 Gateway = 1000
This limit applies to Tier-0 gateway and all the configured VRF on the Tier-0 gateway i.e. this limit is shared for a given Tier-0 gateway and all the configured VRFs on this Tier-0 gateway.
Tier-1 Logical Routers per Tier-0 Logical Router = 1000