I've looked around a little bit but haven't found a list of buffs! The only one I've gotten myself is the main shop 15% discount buff, so could someone link me one if one exists?

Fast Pass and Quick Feet are the only two I can think of.

Fast Pass is during Morostide and allows you to trick or treat faster for a while Quick Feet allows quicker dancing and comes out during the annual Masquerade Ball

There's also the Extra Quests buff. For now, it's only available for the Wizard and it gives you one extra quest for...ten minutes? It comes from an RE.

There's also extra interest buff - you get it every 24 hours if you collect your interest daily.