In devias mate. Near The girl with noob quests for 2nd class. Need 10 lucky coins or 20 or 30 ; pp Never been motivated enough to actually get 10 xd
No public list for the rewards. As @Shameless said, the more you exchange (30>20>10) at once the more chances for better exec items, pets and less chances for getting non-exec items.
You are supposed to exchange in pairs of 10/20/30, not register them as it's been mentioned many times before.
I already tried explaining multiple times to him (in our native language!), it looks like he somehow doesn't get it. Don't know why. Nothing more to do!