Welcome to the Community,
I'd suggest you start with installing ESXi on the R710 host, and then create a new VM on this host in which you install vCenter Server.
Btw. Dell offers a customized ESXi installation image which contains Dell specific tools and optimized drivers for Dell Servers. You can use this image instead of the VMware image if you want ( VMware ESXi 5.5 Update 1 Image Driver Details | Dell US)
You can install as many virtual machines on the host as you want (and as the hardware resources can handle). However, keep in mind that the VMs (OS, applications) may need to be licensed.
André