Your philosophy on backups (and what you are willing to spend on them) should depend on the "value" of your data and time. If you don't value your data or time, you don't need backups at all. If the drive crashes, just replace it, reinstall the OS and press on.
If your data and time is of "some" value but not a lot, then get a cheap external drive and use TM to do backups. It's self-regulating, does a good job. Keep the drive close to the Mac. If something catastrophic happens (fire, flood, meteor strike, etc.) you will lose not only the Mac but the backup, but it's only of "some" value, so you get a replacement and press on.
If your data and time are of "a lot" of value, then get two good external drives and use TM to one for backups, but use a cloner (CCC or SD!) to clone the boot drive to the other. The TM backup is a historical file, so you can go back to any point in time and recover what you had then (in case you accidentally deleted it, for example) and the clone will provide an instant repair for a failed internal drive--you can boot from it and be back under way while you wait for the replacement to come in, and when it does, you can clone the clone to the new drive and be on your way.
If your data and time are "invaluable" or "priceless" to you, then get three drives (or four, depending on your level of paranoia) and use two of them just as described above in the "a lot" category, then the third should be a clone of the TM drive that you take somewhere else to store (bank deposit box, fire and waterproof safe, etc) for off-site storage. Now if you have the unthinkable disaster, you retrieve the off-site drive, clone it to the new machine and you're off and running, only losing what happened after you took the drive off-site. If you are paranoid enough, take the fourth drive as a clone of the boot drive and store it with the clone of the TM drive. That way you can boot from it as soon as you have a new machine and be running on that clone even before you clone it back to the new internal drive.
If your data and time are "absolutely irreplaceable" to you, then put a completely identical system at a completely removed site and get a very high speed connection between that location and your "standard" location and clone both the TM backups and the clone backups from the Standard location to the remote site. The remote site should also have its own TM and clone backups so that if the standard location is totally destroyed by alien attack, for example, you just have to get yourself to the remote site and you are back in business immediately.
Yes, these options increase in cost and technical complexity as you move up the paranoia chain. I personally stopped at "a lot." If I were running a business that I depended on for my livelihood, I would at least be at the "invaluable" level, or maybe even "irreplaceable" if I had enough working capital.
How much to spend? Never spend more than the value of the data and time to recover from it to you. Otherwise it's wasted money. I spent 35 years consulting in the IT industry and I've given the same advice to Fortune 50 companies all across the US. You get it for free!
You're welcome!