ESXi itself doesn't need a lot of storage (around 60Meg) but you do need around 1GB of storage for a normal installation to proceed without any issues and if possible it is recommended to have 4GB available for scratch use. There is absolutely no need for this to be high performance storage but you do want to check the HCG to be sure that what you have can be used. The important point is that it doesn't require much storage and many installs run from USB\SD Flash drives.
All other local storage should ideally be formatted as VMFS and deliver your VM storage VMDK's from those data-stores. You can configure VM's to use physical disks and boot from them if you want - the VM disks are mapped using RDM's (Raw Device Mappings). I've only ever seen this done easily with SAN LUN's, I believe its possible with local disks but there are quite a few hoops that need to be jumped through.
I don't believe it will be straightforward though, the best approach that I can see for you, assuming you are only going to have this one server as an ESXi host, is to make an image of it using one of the imaging\backup tools supported by VMware Converter (listed here), install ESXi and use VMware Converter to convert the image to a VM with its disks converted to VMDKs.