you can buy normal breaks and then switch to Y.

for example lets say you have kazekage gaara and you want to skilltrial him.your goal is to get his golden Y mystery,but you get purple Y instead.what you should do is switch it to correspon plus series skill,and then gather fragments get skillbook skillbreak it and then from skilltrial tab switch it to golden Y.and yes all Y skill are from trial as well as Ls