honestly you can barely call limbus a gacha game. it's got the feature but it just doesn't push the gambling like i've seen literally every other gacha game i've played do. it's perfectly viable to get through the stages with just your base units and i see most people choose this route over trying to get busted limited units like g corp gregor and busted perms like tingtang hong lu for themselves. if necessary, people just grab them as support, which is not a required thing to bring into a battle. sometimes it's even the BETTER thing to do because an untrained high rarity unit cannot fix a difficult stage for you!
your energy gets replenished every time you fail. they've been giving out apology pull tickets like nobody's business. it definitely seems like the story is going to actually END and not be an eternal live service tale! like, i think project moon really wanted to just make another normal game but felt like they had to go this route (the director of the company did literally admit they just needed money). i actually seriously wish they could have. i would have loved to just do a one-time payment.