You can spend these coins on Titles from the Underworld Invasion Boss Event , The Titles are :
January : Time Chaser
February : Party Crasher
March : Mira Chaser
April : Child of Nature
May : Money Chaser
June : Unrelenting Biter
July : Dark Devil Destroyer
August : The Retired One
September : Limit Chaser
October : Invader Defeater
November : Watchdog of Kiri
December : The underdog
250 Silver coin : Friend of Trunks
Lucky Title [From the mystery capsules : Universe's Luckiest.
Title stats :
Universe's Luckiest : Reduces cooldown time by 2.
Unrelenting Biter : 3 Energy
Money Chaser : 3 Soul
Time Chaser : 3 Strength
Party Chaser : 2% Elegant attack
Mira Chaser : 3 Focus
Child of Nature : 3 dexterity
Friend of Trunks : 5% anticrit
Dark Devil Destroyer : 1 props
The Retired One : Increases honest attack by 2%
Limit Chaser : Increases Strange attack by 2%
The Underdog : Increases Funny Attack by 2%
Invader Defeater : Increases wild attack by 2%
Watchdog of Kiri : 3 constitution
Credits to @Roli for the list indeed