I use BackBlaze as my offsite backup provider. It's never given me an error and it was very quick and easy to setup. This is simplest, option I know of for backup (though the also offer some advanced features). They primarily only backup files that you're using, so if you keep files in weird places (not the normal "Documents, Movies, Photos, Desktop," etc.), you'll probably want to look elsewhere. Versions of your files are kept on the server for 30 days.
Being offsite backup, it also means that my files still exist if my house goes up in flames or my laptop falls in a river. (You do have to be connected to the internet and have automatic backup enabled for the automatic backups to work.)