Anything past base Diamond isn't worth it.

Look at the benefits for Diamond Plus (now basically useless, except for the markets which still have lounges), Diamond Elite, and Seven Stars, and you'll see that the spend required to get there dwarfs what realistic benefits you'll get.

Most people erroneously believe that higher tier status equals better offers, but of course that isn't true at all. Offers have nothing to do with tier status.

Base Diamond gets you no resort fees (huge), the priority lines/registration, and also inherits the free parking benefit from Platinum. That's really all you need.