Rich enough to get her + her weapon easily, if you play correctly everyday. Not that you really need any gacha weapon, but missing out on Alpha would be a mistake I think
If we were CN, I'm pretty sure you could get both Alpha and S Bianca as F2P, however global will accelerate the schedule for sure, and I'm not quite sure a F2P will make it for both. Definitely not hitting both guarantee
Alpha is OP and it's possible you'll regret missing her. You need a good physical team anyway and Alpha is significantly better than A Bianca
Meanwhile S Bianca is lightning, she's still one of the best unit in the game but you'll need A Chrome as tank for a good lightning team, and he's only released a month after Bianca S, at the earliest in November this year(?), that's a lot of time waiting for a single actually good team and you'll have to complete ranking and Pain cage without Alpha, that could be a problem, you get a lot of nice stuff by ranking high in this game
If you do decide to skip Alpha, you're left with no great physical DPS. You could use A Bianca in the mean time but she's not great with enemy mobs and that's a lot of the ranked battles stuff.
I want both Alpha and Bianca S so I bought the pass just to be sure. I'm also gonna buy her special skin for her because goddamn.