Time Machine is free, simple, bundled with every Mac and mostly "just works."
Best Economical Recommendation
Use 3 Large HDDs (larger than the total storage to be backed up by 2X to 3X times).
- Two connected as (alternating backup) TM discs at all times. With both set up as TM target discs, TM will simply backup up by alternating between the two every (approx.) hour.
- If there is some big data stuff on local storage that you wouldn't care about losing, you can exclude that from backups in TM "options."
- A third drive "C" is also a dedicated TM disc but stored offsite.
- On a regular basis, eject Drive B and take it to where you have Drive C stored. Swap them. Bring C home and attach it to take over for B as the new alt TM disc. Repeat this step regularly (for me, that's monthly).
The Scenario to Justify 3 TM Discs in This Way
Fire/flood/theft or similar total catastrophe. Such things happen to some people EVERY day. If it was you, your Mac and the backups all at the same location (home) are destroyed/lost. The backup stored offsite can likely completely restore your data to the new replacement Mac. The loss in a catastrophe scenario is the newest data you've stored since you last swapped B & C. In my case, that could be last 30 or so days of data if the catastrophe happened on the day before the swap.
For B & C drive, I use a HDD Dock like this one...
...and store the off-site bare HDD in a plastic HDD case.
Big HDDs are dirt cheap (especially relative to Apple product pricing), so this should not be a near-foolproof option out of reach due to cost for almost any Apple people.
If cost is still an issue, drop one drive and enhance your risk a bit by swapping between what would be A & B drives (with one of those off site). Your Mac drive is acting as an additional backup during the swap time. That's Mac storage + One current TM backup drive with one not quite current TM backup stored offsite.
If Budget is Not So Pinched
Those with a little more budget, consider embracing a NAS like Synology. Synology supports TM and works very well. Synology uses a RAID-like drive system so that one drive can fail and the system can be repaired by inserting another disc in place of the failed one. So that's like TWO backups in one device.
- Synology as TM (main)
- Direct attached A & B drives as extra backups with one of them stored offsite.
- Regularly swap A & B at the offsite location.
The common thread in all good backup scenarios is one, fairly up-to-date backup OFF-SITE. It doesn't matter if you have 50 backups at the same location as your Mac. Fire/flood/theft could completely compromise all 50 backups. But ONE stored away from the catastrophe means you probably never lose much data even in worse-case scenarios. This is the part that most people trying to backup do NOT do. Yet it may be the most important part of a good strategy.