Well it's all about what you're trying to achieve right? If your goal is to level faster, higher max HP (no matter how cheap) doesn't really help: HP is great for lots of things, but it doesn't contribute much to leveling. Imagine if I said "the Boots of Loramin give +80 Charisma for only 20 plat"; sure the ratio is great, but if adding 80 Charisma won't help me level then who cares?
The way I see it the choice boils down to the Platinum Fire Wedding Ring for 5 AC, at a cost of 250 plat, vs. a suit of banded at 91 plat. Since the Shaman already will have some looted gear though they won't get +91 AC from the banded; let's say they currently have 50 AC, so the banded nets +41 AC.
This means our choices are:
- Platinum Fire Wedding Ring: 5AC for 250 plat (0.02 AC/plat)
- Suit of Banded: 41 AC for 91 plat (0.45 AC/plat)
Ultimately you should buy both, because HP does help and the rings are a great deal. I'd just argue that new Shaman should buy the banded suit first, because they will get more leveling power for their platinum that way.
(But then again gear really doesn't matter all that much at low levels, so realistically whatever choice the Shaman makes they probably won't even notice a difference).