If you are going to a job that uses vSphere (ESXi) and you want to learn more about this then you really need to setup a test lab using ESXi and not the free VMware Player or even VMware Workstation, they are completely different. You can download vSphere and use it for 60 days in evaluation without a license. You will probably want to use something like VMware Workstation and build a nested ESXi environment on top of that. If you search the internet you will find instructions for doing this such as http://www.vladan.fr/how-to-setup-nested-vsphere-lab-on-a-pc-by-using-vmware-workstation/
To get the best out of a nested vSphere environment on VMware Workstation then you are going to need plenty of RAM in your PC.
To learn more about the VMware products I suggest you have a look at the VMware Hand-on-Labs VMware Learning Platform
Good luck in your new job and welcome to the VMware community.