I know cost is a factor, but here are some thing you should consider:
#1 The human factor - getting busy, or being lazy, you forget to back up or you put it off and possibly lose some, if not all your data.
#2 Tragedy - If you have a house fire or other serious incident, you would lose all your data.
You could get a NAS (Network Attached Storage) which has an automatic backup feature. They do get expensive, but you're paying for not only the hardware, but the operating system that has features such as automatic backup...and they can backup multiple devices, even your smartphone (with apps that would support this). I have a very large NAS, and it does quite a bit for me. It records my TV shows, stores my photos and downloads, backs up my desktop and laptops, and has a redundant hard drive setup, so if one (or more) drives fail, it keeps going giving me time to replace the failed drive without data loss. I've even added a network security camera to my house and it has software that looks for motion and records the videos. I also use it to stream my music to my DAC.
That covers about 98% of what you need.
https://www.amazon.com/s/ref=nb_sb_ss_i_7_8?url=search-alias%3Daps&field-keyword...The other option is something like Dropbox or other cloud storage. This backups up your data to the cloud automatically, and allows you to share the cloud files from any PC you have the software on. So, let's say I have music on my home PC, it automatically gets backed up to the cloud, so I can also listen to my collection at work on my work laptop, or with the Dropbox app, I can also access all those files on my phone or tablet.
This gets your files *out* of your house, so if you have a tragedy where you lose everything in your house, at least your data is safe and can easily be recovered. The only thing is, this feature is $99 a year for 1TB.
https://www.amazon.com/b/ref=lp_14935779011_spks_0_0_2725887742?rh=i%3Aaps%2Cn%3...You could also do a combination of the above. I believe the Synology NAS even has a Dropbox app, so you could have automatic backups to your NAS, then automatically backed up to Dropbox (offsite). Or, get yourself a NAS, and also backup to your External hard drive which you can keep at work or a friends out (offsite backup).
The cheapest option I could think of right now though, get a pair of Western Digital external hard drives, which should still include their backup software. Have them backup your data every night, and once a week move your latest backup drive to work so you have one at home, and one at work. That still has some human factor in case of Tragedy, but would only cost about $200 for a pair of external drives.