"Done" is very subjective given we're never really done managing a device.
For our enrollment process, I use a custom script that calls swiftDialog and shows the steps and installations being executed. At the end, when all policies that I've called in the script have completed, whether there were failures or not, it waits for the end user to click an "OK" type button. When they do that, I write an entry into a custom plist on the Mac to indicate it's "done" or at least as done as I want it to be during this first phase after enrollment. The script that called and updates swiftDialog loops and watches for that plist entry as well as watching for the Dialog process to close. When it sees both of those conditions, it initiates a restart using the jamf binary and the Mac restarts.
If you're just enrolling your Macs and letting policies run on the natural check-in trigger and not via a wrapper policy like I described above, then using the method @AJPinto would be the best way. Collect inventory, have a Smart Computer Group that looks for all the apps and other conditions you deem required for it to be "done" and then call a separate policy that restarts the Mac. Keep in mind that the restart may not happen for anywhere from 5 minutes and up, meaning on the next check-in, so there will likely be a delay until restart occurs.
