You'll get a different answer from everyone on this. I think TF is the best available of the metrics from Majestic or Moz. It isn't impossible to manipulate, but I think it's the best we've got. CF, PA and DA can be VERY easily manipulated. As a quick example - I have a test domain that I pounded with nothing but shitty GSA links. The only of those metrics that didn't go way up was TF.
That doesn't mean you should buy just based on the TF though. What you really need to do is have a diligent look through the backlinks and check the site's history in Archive.org. I like to look at the whois info too - if it changed hands a dozen times there's probably a reason.
It's almost more art than science. There really is no "if the DA is this and the TF is that you have a good domain". Need to look at everything as a whole and go with your gut.