is there any possibility to just get ESXi deployed and add the same to usagemeter for reporting or having VC is mandatory.?
Officially, there is no support for standalone ESXi. Although it is possible to connect a host directly to UM by configuring it under the vCenter configuration section, the API's are different and we cannot pull the license key from the host to determine the bundle to charge against. For this reason it is not supported and there is no guarantee of correct usage data to be collected OR reported.