I like this article that explains the Rule of Three backups. It's an oldie article, but the basic info still applies. I particularly like how it explains having two different formats and one different location. With all the climate changes of sudden flash floods (Kentucky 2 weeks ago,) and wildfires in drought areas, and of course hurricanes & tornadoes in those parts of the country, you want a secondary location.
http://www.hanselman.com/blog/the-computer-backup-rule-of-three
Google Drive is a good, free, off-site, backup cloud storage. You get 15 GB per Drive account. One is allowed 4 different Google accounts per phone number. I have 5 different accounts as I always liked to split my emails by subject, and now the data is split per subject: personal, business, photos, eBooks, etc.
And if you want to move files from one Drive account to another, you can use the "Share files" Drive function to move files. First share and make a copy on the second account,
then delete them off the first account once you know they are successfully copied and not just shared - and still on the first account. That frees up megabytes on the first account.
My other backup is an external hard drive, 1 terabyte. And once I re-format my old laptop and wipe off many apps that are just bloat now that I don't use it, I will use that as a third backup.