The Ecru Rings are about the only really decent piece of magic tinkered jewelry, and you need to be REALLY lucky and get something like a 1/2 ring or high HCI or DCI, for it to be really useful.
The Ecru rings are the ones with 50% enhance potions (used to be75% before the 'new' cap)
And on a side note, you only seem to get the EP about 60% of the time, AND even with a +26 tinkering tally and GM tinkering, you only succeed 76% of the time, thus lost resources. (forgive me if my percentage is off, I am at work and cannot double check that)