Originally Posted by Zandel

If your only interest is gold then the 80 stam gold mission is the best stam to gold ratio and that is including selling all 2* girls and playing the normal gatcha and selling those too.

If you want XP and gold tho it's not a good option.

But neither is the ultimate event mission. The exp/stamina ratio is barely better in exchange for a much worse gold/stamina ratio (even if you sell all the girls from the seeds), so I'm not sure what the point is in playing the ultimate mission besides the skillblooms, unless you need to dump stamina before leveling. I think if you can clear the ultimate event mission, you can clear 12-3 if you're concerned about exp or do the gold mission if you don't care about exp. The ultimate mission seems like a middle ground that's just worse. And if you can clear it, 12-5 is way better than the ultimate mission, although it's probably harder.

80 stamina gold:
~22k gold
160 exp -> 2 exp/stamina
275 gold/stamina

120 stamina event:
~20k gold
~2k seeds
300 exp -> 2.5 exp/stamina
167 gold/stamina
17 seeds/stamina

12-3 (35 stamina):
~3k gold
~600 seeds
473 exp -> 13.5 exp/stamina
86 gold/stamina
17 seeds/stamina

12-5 (40 stamina):
~5k gold
~1000 seeds
560 exp -> 14 exp/stamina
125 gold/stamina
25 seeds/stamina