5 copies of your data are better than 1 copy. 10 copies is better than 2.
Ideally I recommend a online backup service (these can range from $5.00-15.00 a month) for unlimited storage. I recommend online backup services because they are automated and require very little attention after initial setup. I have personally used carbonite , idrive. (Look over their perspective services closely) as they are different.
For those who hate a monthly cost, I will even recommend a jump drive or a secondary internal hard disk. This method works although it may take some user input.
The 2 most common reasons for data loss include Ransomware and drive failure.
Please take note (All hard drives will fail at some point). Ideally with a backup service in place you can be proactive so when your drive does die, your loss is minimal.
With the newest threat of ransomware your data can be corrupted to the point of return with one bad (click) on the web. When this happens your options are restore from your backup, or pay the ransom. I have seen already where this ransom could cost you significantly more that a years subscription to a online backup service.