why would you do that ? You still have 6 more days of the event. Dont spend it unless you really feel like you cant make it in time for what you want from the shop. As for the manyus - dont. Its not worth it. Plus you can pick up nice juicy lvll 100 manyus from the shop.
I personally almost always ignore events on the two days a week when Manyu comes around, but would not refill my stamina with FGems. The rate we get those is so low that it simply is not worth it.