How to organize a cloud of several nas in different locations?

Question

NAS

There are:
1. MacBook + external HDD, on which fresh photos and videos are regularly uploaded
2. WD MyCloud in one apartment
3. Buffalo router (you can install OpenWrt or Dd-wrt) with the ability to connect HDD via USB, in another apartment
All three points - are located in different places. I want to set everything up so that the photo / video from location 1 is uploaded to locations 2 and 3. Or at least - only to location 2. Preferably - without any dancing with tambourines, automatically. I copied the files from the fotik's flash drive to an external HDD - and forgot, then everything is synchronized by itself.
How to solve this problem reliably and budget within reason?
He himself began to look at WD CloudMirror, but it seems that he still knows how to synchronize with a computer / disk, but it’s not clear how he can synchronize with another location.
The options "to assemble a server, roll the OS there" are being considered, but so far only as theoretical ones. I want a ready made solution.