I think October is the best month. It is not only the beginning of Autumn proper but also Halloween's month. In addition, you can buy Animal Crossing Bells from ACItems at the best price this month. Animal Crossing: New Horizons is a good place to celebrate this season because it has pumpkins that can be planted, a large number of spooky-themed decor items, and new Halloween items available! They are as follows:

1. Spooky Trick Lamp
Buy from Nook's Cranny for 11,600 Bells
Made with a DIY recipe of 4 Orange Pumpkins and 4 Iron Nuggets
Orange, Yellow, Green, and White pumpkins can be customized
There is a door in the front, you can see a vignette when you open it

2. Spooky Treats Basket
Buy from Nook's Cranny for 10,000 Bells
Made with a DIY recipe of 1 Orange Pumpkin and 2 Candy
Orange, Yellow, Green, and White pumpkins can be customized, each pumpkin has its own face (two pumpkins of the correct color are required)

3. Spooky Tree
Buy from Nook's Cranny for 10,000 Bells
Made with a DIY recipe of 5 Orange Pumpkins and 10 Hardwood
Orange, yellow, green, and white pumpkins can be customized, each has its own face (the white version also makes the tree white)

Have you already purchased these Halloween items? If you don't have one, you can buy Animal Crossing Bells on ACItems and go to Nook's Cranny to exchange for these items or directly buy Animal Crossing Items any you need on ACItems.