Regardless of whether you use a NAS or just a standard external hard drive, the principle behind using either of these is the same...as Wainui said...

If you're going to do it, commit to it and do it. Setup your backups/syncing etc. First between your PC and one external drive and then between the 2 external drives.

Get into the habit of making sure that once the copy of the 1st drive has successfully completed to the 2nd drive, move that drive to a different location... at the very least (and if possible) move it so a separate part of the house or get a safe (doesn't have to be fancy) just secure, difficult to break into and/or move etc...

Of course how far you're willing to go will depend on how important your data is to your and how much data you have...

If all you are worried about are things like photos and personal documents, then OneDrive, Google Drive should suffice (you can sync to both to have 2 copies). then of course there are online backup platforms, such as iDrive etc.