What gs items is your bard using?

[kmoustakas]

I'm assuming at least an sp and a hp item. Co-op would probably be one of the options, but what else?

[Franke]

Conc-opp sp goggles, Min II hp cloak, GS Rapiers ; Min II, Rad II, Lit II. Not played it in a while tbh though Swashbuckler will likely change that...

[Rull]

I can highly recommend the following:

Tier1: 10 HP, +2 str skills
Tier2: 15 HP, +4 con skills
Tier3: 100 SP, +6 cha skills.
Concordant Opposition (6 WIS, SP regain)

Because Tier1 is pretty bad for SP
Tier2 is also bad for sp, netting only 50 SP compared to 15 HP
Tier3 however is a much better deal, 100 SP instead of 20 HP
But the thing that really makes this item work is that the 100 SP also gives you +6 UMd/perform/etc.

As for which slot, that is debatable. I definitely would not go with gloves or bracers. I would say boots.

A second GS item is not worth the gear slot, at least not on levels 18-28.