Let's first find the Earthen Drums , items that allow a free use of the powerful Quake spell. Go find the guys up north speaking about Chocobos and items: nearby, you'll find the two hidden Earthen Drums .
As for the shops...
The weapon shop is interesting for your Bard. Each harp allows a different Song to Sing. The Madhura Harp raises Defense; Loki Harp raises Attack; Lamia Harp deals damage; and Dream Harp restores HP. All of these attacks or modifiers range in the 10%~20% of actual Attack/Defense/HP. Purchasing one of each if you are investing in the Bard is not a bad idea (but if you don't have the Gil, Loki or Dream Harps are good ones to pick).
The armor shop has a Feathered Hat , which is one of the best hats you can have so far. The Viking Helm, Dragon Helm, Chakra Band, Black Cowl, and Scholar Hat are all better, but also more job-specific. The Feathered Hat works for everyone! So consider that.
The Gaia Vest for Geomancers and the Bard Vest for Bards are also pretty good, but specific to that job, more or less. The Rune Bracers are allowed for the more magical jobs, prevent a few statuses, raise magical stats, and are a good buy for your various mages.
After you're done, leave town.