Newegg has the Acronis True Image 2017 backup program on sale for $9.99 after a $30 mail-in rebate. See here. It is for one device, and works for a Mac, PC, or iOS device.
I've used Acronis to backup my PC for a long time, and it seems to work well (in theory, anyway), because, thankfully, I've never had to use it to recover from a failed disk. I've not used Acronis on a Mac, but I'm sure it would work just fine, as Acronis has a good reputation.
Just FYI, be aware that probably next month Acronis will come out with their 2018 edition. This won't negate the effectiveness of the 2017 version. Whether you use Acronis or another backup program, I highly recommend that you do a clone or image of your hard drive just in case you might have a hard drive failure.
Is this likely? No. Is a fire on your house likely? No, but you carry insurance just in case, don't you? That's why I'm a big believer in a full, bootable backup for my hard drive. If your hard drive failed, could you easily live with this, or would this cause you considerable anguish.