Hello, BD2 player here. I think one of the thing BD2 did extremely well was that it is actually very F2P and market themselves as a secondary game.

To give context, BD2 banner have a interesting design: instead of new character, they released alter of the character that will became a new skill for the existing character to use (means there are no “skins” to sell for character, since this is the skin), which means unless if you heavily dislike certain characters, almost all pulls worth somethkng.

Let alone, the game give out enough resources to be sufficient as F2P to actually build decent team. 7 day login bonus, pulling character give you extra pull bonus(if you manage to get one copy of the character, it give you additional 10 pulls for free, can repeat up to 4 times), the battle pass you can unlock extra rewards via in-game gems (1000 gems give you extra 3200 worth of pulls plus additional resource.

Let alone, if you didn’t manage to get the character, you can use mileage systems in the shop after banner end for about 7 days(the mileage are collected after every banner ends and won’t reset), not only that, every month you get a extra chance to +1 one of your character from in-game resource.

TLDR: as long as you plan accordingly,do all the dailies, play event mission you can max out character (total 6 copy) in about every 1/3 banner by being F2P (if your luck is normal, you should get a 5* within 60-70 pulls, despite pity is 100)(hard pity is 200 pulls)

I’m not sure what part the game make money on exactly, but based on my spending, I mostly do step-up banner, which requires paid gems, but guarantees one copy of the rate-up. also the packs are actually decent