I just wait till my 40 stamina map farming will spawn a boss (took me 8 runs today lol for first spawn), then I just use that single 2* to poke it, share it, and poke it 1 or best case 2 times more. If I spawn them more often than RB regenerate, then I just wait for RB single poke and share, people will poke/nuke them - doesn't matter to me - all always die so I'm fine. And I don't care if I use 3 RBs on a shitty 40lvl boss, cause I care more about doing daily quest than getting more shards for equip gacha.