Here are some ways to get wonderfuls:
1. Win them at festivals.
2. Every odd numbered time you get 2 the last floor of the mine, the Harvest Goddess will give you a wonderful based on your farming degree.
3. You could buy wonderfuls at Chen's Shop in the winter.
The date matters when Chen's selling wonderfuls:
Winter 1-6 = Red Wonderful for 2000 Gold
Winter 7 = Indigo Wonderful for 50000 Gold
Winter 8-13 = Yellow Wonderful for 3,000 Gold
Winter 14-19 = Blue Wonderful for 2000 Gold
Winter 20-22 = Green Wonderful for 3000 Gold
Winter 23-25 = Orange Wonderful for 5000 Gold
Winter 26 - 30 Purple Wonderful 2,000 Gold
The rank of wonderful from worst to best: Blue, green, red, yellow, orange, purple, indigo.
Anymore questions, just ask!