Use 20 of them to get Jackbot to 1 Star and unlock the Equipment Drop Chance skill, because that makes him an even better farmer and also there’s no easy way to get Jackbot shards even if you’ve unlocked him; they can appear in the Summon Gates once he’s unlocked, but with a 1/15 (if you don’t have S.I.M.O.) or 1/16 (if you do) chance you’ll be lucky to get even 2 shards with the weekly free summon gates
If you have more Gym Passes,
- You could use them for Open A heroes if you have been using them as your primary heroes for a while, and are finding it hard to progress with them because their shards no longer drop in the castle - especially if you are close to 5 Stars
- You could use them to star up Jackbot even more - which will allow you to use him to farm higher levels (however, in that case he will be less effective in lower levels because you’ll often clear the level before you can get the 15 Jackbot Proc’s)
- You could use them to star up S.I.M.O., or one of the Premium Heroes, because it’s hard to get their shards any other way, but I would consider it less useful than starring up Jackbot
- I would definitely not recommend using them for Open B heroes (you should be able to farm castles for them)
In any case, don’t use the Gym Passes until you have enough to star up the hero - better to keep your options open
