Biggest threat todays world is to protect your data. Assuming a small-medium-large office environment there may be different types of setup. If money is not the problem always go for server-client environment register domain and use vpn to protect your data. If using p2p setup use atleast vpn to share files and antivirus is must for any kind of setup. Don’t download any unknown unwanted file type specially zip and exe’s that are the common file type to spread ransomeware and other trojans always consult with it team before downloading anything from internet specially any software. If possible turn off usb connections for some client pc’s .