I'd say it's best to rely on getting bloom dragons from events and whaleship exchange if you can.

Otherwise, you're stuck with the bloom dragon stages. The rates for the lvl100 bloom dragons are quite bad, but it's still probably better to do the 80 stam one over the 50 stam one since you can get 4 chests instead of 3. Idk if the rates are better in the 80 stam one, but it certainly feels like it is.

I see, but events do they still give bloom dragons at all? the current one for eg, i cant see bloom dragons

okay my bad, line up 8 seems to have plenty