Knowing the full cost of the recipes, you should be able to look at the price of materials in the bazaar and find which of the 4 will give you the most cost effective final formula. You can also think of it like this: If the market is 100pp for tungsten, then 85pp for cobalt, 50pp for titanium, or 20 for tantalum is functionally the same for getting skillups. Based on the EQTraders calculator, trying the harder 2 recipes will have less than a % difference in skill up chance, which is small enough to be inconsequential. If you've got a 400 or higher prime stat, that difference goes away.
I, so far, have been able to make five banded helms, and two banded shirts. The shirts I did at with my skill of eighty. Two tries per shirt. I know I was lucky to only have a single failure per item. But it goes to show you that having the patience to walk the long road will pay off. With the going rate being about forty plat for a shirt, if not more... You can see that even with a few failures per item, you will be making your gold back, and more. Don't just worry about getting to the skill to make banded, and stopping there. There are rumors around that smiths shall soon have the ability to start to make plate, or a type of plate armor. I have also heard that you are going to need a skill up around one hundred and thirty, if not more, if you want to pull this off.