I'll quote what I wrote on tumblr when someone asked me about this once...
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I am going to quote Animal Crossing Wikia on this ^-^
"To upgrade to T&T Emporium, the player must spend at least 100,000 Bells at T.I.Y., complete four Gracie Fashion Checks and have had the store open for at least 30 days. Gracie doesn?t appear at your town Plaza until you have spent 70,000 bells at T.I.Y.?
I put the important part in bold.
I am unsure if you have to spend the 70k in store or if purchases from the kioski counts towards it as well?
And if you wanna cheat a little and get Gracie Fashion Checks all done in one day try this method? But be wary, it is TT 1 day each time so there is always the risk of a villager going in boxes without a ping notice. I also have not tested this method myself, but I have heard from more than one source that it works.
1. Load your game and Gracie at Plaza
2. Complete her fashion check.
3. Save - quit
4. Set time to 5:59am that day
5. 6am hits, ?new day? starts
6. Gracie will be at plaza.
7. Complete her fashion check
8. rinse-repeat until it is completed the 4 times.
Btw, 4 characters who complete it 1 time each does not count.
And you only have to have 1 character complete the check 4 times?
It is also important to remember that when she shows up is random. Kind of like whenever Katrina, or Redd show up. It?s random and you could go weeks without her showing up. That is why many people prefer to do the TTing method.
Personally, in my old town I just waited it out? I?m one of those people who aren?t huge in TTing or things like that, but to each his own."
I can't say for sure that kiosk purchases count, but after taking around four months to get the Emporium in my first town, I decided to buy a crown from the kiosk every week in my second town. Without TTing (well, except once when I was TTing a villager into boxes), I got all four checks done in around 24 days.
Most may balk at spending a mil on crowns every week, but it was worth it to me.
It took a while of having T.I.Y (weeks) before Gracie showed up in either of my towns. I never heard of the 70k limit before, but I've been trying to keep track of how much has been spent in my second town, and I thought I was at about 60k+, and Gracie finally showed up today. So it seems like it's accurate.
I got T.I.Y in around 3 months of playing. I didn't get the Emporium until a few weeks ago (around a year of playing). Really, it's just luck. The first time I saw her I had Streetpassed a few hundred people, so maybe if you Streetpass someone with Gracie she'll appear in your town?