Does anyone have the marble key producing dragons? Is it worth it? I am contemplating but I'm not sure even 3 keys per day is worth the cost. At this point that's basically one extra slot per month since I have hit the point where it costs 40 keys to clear a new spot.
What about the food producing dragons? Right now, I have 800K food....so again, not sure how useful though at least with the food producing dragons I do always need food, whereas the map and marble key producing ones I will not always need.
The gold ones are a no-brainer for me, though I do consider how much they cost vs. how much gold they give to decide - I like to break even in 6 months or so, though I may up that since it seems I like this game enough that I will be playing for a while.