Do not do the bonus stages.

Summoned stage: minimum 2 runs = 345 x 2 = 690; 690/10mochi = 69 per mochi
80 stamina stage: 485 + 8 mochi = 1037; 1037/80 stamina = 12.9625 per stamina
80 stamina bonus stage: 630 (I didn't do it myself yet but someone said this), 630/80 stamina = 7.875 per stamina (still need to beat 1037 even if 630 is wrong)

Plus, you get other rewards from doing the regular stages, like coins and crystals.

Also don't know how people can do the summoned stages 3 times. The fastest I can do it is 35 seconds per run. Maybe I need to make a squad with just 1 fast team. Means I need to get rid of one of my nation-based squads and remake it whenever their nation missions come up.