How it works
One blow takes 0.55 seconds. 
Mastery level 22 in Buffs adds an Auto Bubble Blow option so you do not have to hold the button.
Gum has a capacity. When it is full you cannot blow more until you sell at a Selling Area, which pays out the current world's currency. Better Gum from a Gum Store raises the capacity.
Flavors, bought from the same Gum Stores, raise how many Bubbles each blow gives. Pets with a Bubbles stat, potions and other buffs raise it too.
Trivia
- Before Update 2, Bubbles could be blown while eggs were hatching. That exploit was patched in the update.