I would keep my FS. It's too precious and multiple copies are not that usefull. Another equip slot is good when you have all 4 unlocked or if you plan to use 6* equipements but I'm not sure it's worth the FS.
I did get some dupes sometimes but only when I was 1 roll away from the ticket.

Congrats for lvl 191. Did you already beat the level with a 90% evasion boss and insta-kill intercept? I don't remember what floor it is.