@hotnoodle No idea if there is recommendations list or not. I can recommend certain castles but the gacha is very random and there are so many characters inside. We probably won't have the same shiromusu.

Just my advice, get a castle with Ki generator. Deploying shiromusu and upgrading them during combat requires Ki, so just having 1 of them in your party is a big advantage. :)

Higher rarity is better of course. Maps has terrain and deploying girls that match that terrain will give them bonus stats. The guides already cover pretty much everything, if you have more question, feel free to ask around. :)