24 hours * 20 = 480 stamina per day
If you get most gatherings 9 * 20 stamina per gathering = 180
Summing we get 660
Which means 330 tickets a day with mediocre gathering and no level-up refill
7*330 is 2k in a week and that is for phase 1
As mentioned above phase 2 will be easier to gather tanzaku papers by about 50%
We have more than enough time to reach 4k