Level : 1,2,3,4,5,6,7,8,9,10,11,12
Gems : 13 to 123
We have to increase from 13 to 123 over a span of 11 levels.
That's an increase of 110 over 11 levels.
110 / 11 = 10
So we go up 10 gems each level
Level : 1,2,3,4,5,6,7,8,9,10,11,12
Gems : 13 23 33 43 53 63 73 83 93 103 113 123