Just read the info of the event. All 12 gacha pages (starting and 11 resets) are fully listed. Price and what is inside them.

Also if one is able to run Advanced or Ultimate map, one can practically fully clear all pages just with passive regeneration and gathers. Even easier if you level up few times.

Clearing Ultimate map on 3 medals wasn't that hard. Put two similar speed teams bottom. Put 3 teams on top-right if you want to use both uses of the canons. With 600 speeds on bottom teams, they will kill bosses and reach end-flag around same time as 400-500 speed top squads reach their teleport.

EDIT:

Can someone post a print screen of that 10 GF 0-stamina bonus stage. I am wondering what team set-up to have for it. Like is 1 squad enough like the "broken" event with repeatable -stamina map few events before, or do I need two, or all 4 + helper.