Gacha games thrive on their predatory practices, fear of missing out, obfuscated costs, skinner box gameplay loops.
Unlike the current "Celestial" Gachas this one more accurately matches the predatory style of Gacha. Instead of Tickets with better or worse odds, all rewards are grouped by source/theme/effect. An example would be the banner. "Devils of the old school building" a banner which includes all characters, Sacred gears, relics and so on from specifically the first volume of Highschool DxD. Or the "Natures Guardian" Which would include all the abilities, skills, powers, artifacts, of a World of warcraft Guardian druid. Banners can be rotated at will (And reverted for review purposes.)
Pulls cost 160 gems,(1500 for 10)
Pity increases the odds of getting a Headline or "Sub-Headliner" reward from the Gacha. In the above examples, The "Boosted Gear" would be a headliner reward, with "Rias Gremory" as a familiar as the sub headliner. After 150 Rolls without a reward Pity will roll one of those two on a 50/50
If enabled (on by default) every time the Gacha banners rotate there is a 75% chance that an event will occur this can be something like 50% bonus pity (Every 100 rolls), double 5 star rolls, Extra rewards for rolling a certain number of times. An extra event banner.
Another element of Gacha missing from most stories is the lack of junk rolls, sure they get bad powers from low tickets, but they are rarely entirely wasted. So we introduce 2 elements to rewards, both pulled directly from the Gacha Game Genre. Condensation and Enhancing. All rewards are given a number of tags, these tags determine what "Junk" rolls can be used to enhance them, increasing their power incrementally. Using the "Rias Gremory" example, we could give her the "Student" and "Devil" tags. Then throw into the banner a number of "School book", "School Uniform", "Devil Contract", "Summoning Flier" Items, that also have that tag. Condensation lets you improve a reward significatly by sacrificing an extra copy of them. (In the case of companions, they instead have a "Soul Item" drop in place of extra copies to clean up the morality issues)