I just opened 25 bags earlier today myself.
9 bags contained a bundle of 10 crowns (the item you need to collect for the current event)
5 bags contained ambrosia (the item you can use to level-break your units)
11 bags contained crap like luna/brave points/ally points.
Leana's Exchange Shop is the only place you can get Ambrosia, except as a prize in events. The event items it provides is also pretty darn useful if you have a target you want to reach and you're coming up short in grinding for it.