Time to vote on the limitations and ideas set by all of us!
Due to the fact 100 rings are viewed as a hard to obtain, however 10 rings aren't I'm gonna have to say I want to go with a traditional U.S style system. 1 ring is valued at about a penny range. So basically it would go like this
1 Ring = 1 Dollar
1 Super Ring = 10 Dollars
1 Ring Capsule (Sonic Riders) = 50 Dollars
1 Red Ring = 100 Dollars
It works out pretty well. Cents would be completely removed from the equation though.
For transformation I say 1 ring is 1 minute. 500 are needed to transform
Currency: No comment.
Anywhere from 5 minutes to an hour, 50 rings.
Transformations shouldn't last for longer than an hour (For Super Forms) or 50 minutes for hyper forms and as for charcters with smaller forms (Super Shields) about 5-10 minutes.
And the natural way, 50 Rings
I agree with the currency Blu put forward though Red Rings should be for other purposes and 100 dollars should just be a 100 Super Ring. I also think Rings should be the worldwide currency.
As for transformations, power from a ring is drained every 12 seconds, so if one had 50 rings it would last 10 minutes. Also, I think 500 rings should activate transformations.
I think Blu's currency system is good, I think currency should be world wide too.
Though red rings could be used as the transformation rings, 1 red ring would allow you to be transformed for 5 minutes.