I have no idea why you are installing esxi on a bere metal machine but i presume you want it for a home lab.
Well from my experience, when i first started learning Vsphere 5.1 - All i did was install windows 7 on a Desktop - then bought Vmware Workstation - I installed 5 ESXI host on it and tested all the features (HA,DRS,FT,VMotion etc) .
I have an i5 Desktop 2T Hard disk, and 32Gb Ram - but you could look for at least 8Gb Ram it will work fine.
Let me know if you need help setting up Esxi on Workstation..
Regards