The challenges I usually do on my own is this:
1. Do not time travel so often.
2. Only sell Fish to CJ and Bugs to Flick whenever they visit the island.
3. Do not buy or sell Turnips since it makes it too easy to earn bells.
4. Only sell Blue Roses and Gold Roses to make a profit on Bells, but make sure its only at the Drop Box at Nook's Cranny
5. Do not Restart the island until the season changes to Winter.
6. When villager hunting skip a villager that you had before and if you see a villager you never had before and they don't show up on the Posters in the Nook Shopping app they must be invited.
7. Only talk to your villagers by gifting them wrapped gifts that contains Non Native Fruit.
8, Once you get a Villager's Photo they are allowed to leave, any villager who hasn't given you their photo must stay until their photo is given to you.
9. Only have Gold Roses and Blue Roses on your island. Any flower must be digged up and thrown away.
10. Whenever a villager lives on your island their home must be decorated the day after they moved in. Outdoor interior themes are not allowed and must be reverted to a regular home interior.