The guide is not up yet, but not having Achen's guides for card flip events is not the end of the world by any means. Currency needed honestly depends on what you honestly want to get and if you use the cheat sheets or not.

I will post it when it becomes available, but in general...
- Phase 1: gives currency; Normal special gardens
- Phase 2: More sheets open up, more currency, event special gardens

Every day a new bonus sheet will become available.

Good luck