I agree that Manager Girl is a useless, annoying character and her only good point is her body, but I like Gambler Girl and find her funny, so will defend her.
In my opinion, Gambler Girl ability will affect drop rate and also affects the events of the story, in other words, her class might be a physical manifestation of the absurd and rare events that only happens to the protagonist party and allows them to discover hidden places full of OP treasures.
- Her reckless behavior led to her capture which kickstarted a chain of events: Archer Girl fled to the 1º floor on the EXACT MOMENT the MC was inspecting the door. This led to Sword Girl and Archer Girl joining MC party and killing the boss thanks to the COINCIDENCE of MC being the perfect counter to the boss physical immunity. The event made them rich and full of prestige to the point the party got a quick promotion ON THE SECOND DAY.
- Her reckless action of using her special move together with the Archer Girl was the only reason they found this hidden dungeon since her special guarantee a 100% success rate to the next special move. And since no one was going to enter the teleport device, her luck acted once again to force the party enter dungeon before anyone else did got the treasures. We all know that they'll face a strong hidden boss and get OP treasures on top of another promotion ON THE THIRD DAY.
Remember guys, its only three or four days since those people reincarnated to this world and the MC is already rich, got many strong items, got a harem full of beautiful girls, got a rank promotion and Sword girl finally found a big party that will accept her and rescue her friend and its all thank to Gambler Girl being reckless.
So praise Gambler Girl sama you heretics.