v.134 - Super 8th Anniversary Update Highlights

But after that? it will be valuable....

The ring gives 2% and it's off base stats, like Justin said. If you're training in a party play area, you'd get

Without Ring:
100% Base EXP
010% Party EXP (I'm pretty sure you get 10% just for being a party and killing in the same map as a party member)
250% Party Bonus EXP
-----------------------------
360% Total EXP without Ring

With Ring:
100% Base EXP
002% Ring EXP
010% Party EXP
250% Party Bonus EXP
-----------------------------
362% Total EXP with Ring

The difference between the EXP is 362/360 which is ~1.0056 which is less than a 1% increase in EXP.

This basically means you'd get the same exp in 59 minutes and 41 seconds with the ring that you would get in an hour without the ring, so you save 19 seconds every hour. Every three hours you train, you save a minute, and you'd have to train 180 hours before the difference between having the ring and not having it is an hour. The time you save would become even less if you add in the Mercedes Link or even an EXP potion.

In a normal training area, you'd get 102% EXP instead of 100%, so the difference is a straight 1.02x multiplier, which means you'd get the same EXP in an hour without the ring that you would in 58 minutes and 50 seconds with the ring. You'd save 70 seconds per hour, and an hour every 51 hours of training.

I think the difference between having the ring and not having it is pretty small, the time you save is so minuscule, especially compared to the time you've already had to be training in order to get that savings.