There's a video on youtube claiming that if you roll 1 silver or 3 bronze girls in the normal gacha, then the next 10+1 roll you do will have a better chance of loot. Now, I don't know whether that is true or not, but the last two rolls I did that way provided me with 5 gold girls which is better than the previous two rolls, which didn't give me any. In all likelyhood it's just luck, but if the girl pool is connected in some way, then there's a possibility it's true.