What non-essential directories can I exclude from TimeMachine?

I want to have the most # of backups of my actual files, not of temporary files, and easily restorable data.

• What can I exclude from a Time Machine backup to get the most efficient backups?

(I use VMs, so tips for Parallels, Virtual Box, etc, are welcome)

In the sample below, I blocked

• Backups of all Drive sync technology (Google Drive, One Drive, etc)
• Xamarin project output (in the Simulator). All this is stale cached data
• iOS emulators with Xcode.
• Stuff in the MacOS app store
• Stuff in the iTunes App Store
• Backups of my iPhone devices

Solution 1:

Most efficient backups would mean leaving Time Machine alone, not twisting knobs randomly.

The only thing you should be excluding are the VM's.