that's the whole thing... rainbow medals are meant to be obtained from that leader ticket gacha... cause even 6* dupes from the premium gacha is meant to be chump change compared to the rainbow medals you can get from leader tickets...

which sucks too cause there's a way to get leader medals now, and it's not hard if you got a strong team (my best is at 150k offense and they all have weakness maxed out as an ability)