What's a good range to spend on blue building quests? I can't seem to find a guide for the blue building with the rank caps or blue point values or anything. The items in the blue shop vary wildly in sP price to blue point price so that's not a good metric either.

What do you think? Is it worth to spend a lot for the rank-ups and points?

honestly I just don't do any of the expensive quests, especially if it's asking for subq or a really expensive elixir/plushie. If you have good internet, moving up in rank probably takes more patience than anything, but someone with more experience would probably know better lolllll

I usually have a bit of disposable SP but my cut off point is 150K for all items. When I start a quest I bring it all up in the shop search and have a look at how much its all gonna cost before purchasing anything if its around 150K or below, I buy it. If not I quit it, when you complete a quest you generally go up two ranks so I have no issues cancelling the odd one :)