You’ll just want to connect a NAS to your router (I highly recommend Synology). If you’re pretty good at navigating operating systems, you’ll be fine with Synology. Just go into the file sharing settings, then enable SMB or FTP (whichever you prefer, FTP is faster, but SMB is more likely to be supported across platforms). Then on your client device, enter the IP address of the Synology (you’ll see this on the Synology dashboard) along with the username/password that you set and you’ll be in! As long as you have a decent router with low interference from neighbors, your media should play wirelessly without buffering.