You have to pass four checks before you can upgrade the shop. I don't know if you know this already but if you don't any have clothes or accessories to pass you can use any extra characters you have to ask Gracie for a fashion check. She usually gave my other characters a different theme. I think only on my last check did she want the same theme from my main and secondary character.
Also, Idk if you time travel but if you do you can get Gracie's checks done without waiting for her to randomly appear. On the day she shows up pass your fashion check and time travel to 5:59 am on the same day. Save and quit. After that I TT'd to 12 pm (on the same day) and Gracie was there. You can do that until you pass all four. Be careful though because while I was TTing one of my villagers asked me to move. I have 10 villager though and like every 4 or so days someone asks me to move.
just a tip, gracie will refuse to give you a fashion check if you have bedhead
and hairstyles do not have a theme in case you were wondering
you can always get basic clothing either in-game or from someone else on here even on the next day you can time travel back to gracie, that always worked for me at least
