The best way for evaluating the Software is by using the evaluation period of 60 days after initial installation and powering on the ESXi and vCenter.
The type of the vSphere Edition depends on your needs or to make it short if you have a shared storage around to technically use of VMware HA, vMotion or other stuff?
If not than the small Essentials Bundles should be the right one (around 500 bucks onetime costs and 65 for every year to take the Subscription alive(give you every new version for free).
The main reason for customer who buy this is to unlock the APIs to get 3rd. party Backups working and getting a vCenter.
If yes... maybe the Essential PLUS Bundle should be the right one. But costs goes up to 4000,- for license and 1600,- for a 3Y Support and Subscription. Please take notice the SUPPORT.
Regards,
Joerg