Edited by wolyeon265 at 6-28-2014 09:01 PM
While on this topic I thought I might as well give out some math to make things more clear.
Gems spent for full spin is 900.
Max reward is 3050
Min reward is 305
The expected return is 1*305+2*305+4*305+... summing up to
10065 divided by 12 = 838.75 at the cost of 900 equating to
0.93194444444 rings per gem
Now compare this to other ways to get rings at the cost of gems, this is probably the most profitable.
The other obvious ratio is the 400 rings for 1000 gems, 0.4 rings per gem.
Another way to get rings with gems is the tavern, or the plus sign next to your rings. This is probably the worst
Doing 1 round of rock paper scissors cost you 150 gems and you have a 1/3 chance of getting 150 gems(break even), 1/3 chance of getting 5 rings, 1/3 chance of getting 20 rings
thus with 1 round of RPS you have a net gain of 5 rings for 150 gems, or 1 ring for 30 gems, giving you 0.0333333 ring per gem. which is HORRIBLE, NEVER EVER EVER DO THIS.
2 rounds of RPS's math gets very complex, but lets take the best case scenario. 2 wins for 300 gems would net you 40 rings for 300 gems. giving you 0.13333 ring per gem. Still horrible in the BEST case scenario.
Obviously it gets better as you win more consectively, but for you to break even with lucky spins you need to win a lot.
3 wins 450 gems 80 rings
4 wins 600 gems 160 rings
5 wins 750 gems 320 rings
6 wins 900 gems 640 rings
7 wins 1050 gems 1280 rings
8 wins 1200 gems 2560 rings
Obviously if you keep on winning ONLY the expected return will be humongous. but the likely hood of that is slim.
3 wins 1/2^2
4 wins 1/2^3
x wins 1/2^(x-1)
so for you to exceed lucky spin you need to have x = 7, giving you 1.56% chance of getting that result.
*I'm using 1/2 because 1/3 of the time nothings happens, therefore 1/3 of the time you win 1/3 of the time you lose, thus out of the 2/3 of the times that makes an influence 1/3 gives you a win, which is 1/2 probability.
To sum up, from worst to best
Rock Paper Scissor for ring 0.0333 ring per gem
Buying rings from store 0.4 ring per gem
Lucky Spin, equating to 0.93194 rings per gem
So moral of the story. Always spend 900 gems on lucky spin.