New To FortiManager

I'm new to the FortiManager. We initially will manage about 5 FortiGate 60D's with the FortiManager. I believe that all the 60D's are at firmware version 5.2.3. We plan to use a VM version of the FortiManager, likely hosted using Hyper-V. I see that firmware versions 5.2.0, 5.2.1, 5.2.2, and 5.2.3 are available. Which firmware version should I select? Is newer better?

Any other suggestions for someone just starting out?

Thanks!