Thought of that but the idea of waiting through 5 upgrades isn't appealing either. Plus I don't see any prize worth tearing out something to build a different something that I will then tear down to put the original thing back. If there's no short-cut/work-around I'll just stop on that step. But thanks for taking time to respond.
I had the same problem... except it was in the quest to either complete 2 researchs or upgrade 2 buildings to level 12. I've just started Sorcerers and Dragons and didn't look far enough ahead to see that I was going to need to complete the 2 researches. I only had one research left that I could complete until I actually build more than the campus and wisdom square (as far as I'd gotten before the event started). All the rest of my space is tied up with level 1 stuff to make it possible to do the event. All my buildings (residences, workshops, military, factories) either need research to level up again or more space than I have available. So, what to do? I used 2 - 2x2 spaces and took two of the buildings that I'd already had to take up to level 4 for a previous quest and I'm leveling them up to level 12. I'm doing 2 so I won't have to wait longer but I suppose you could get away with just a single 2x2 space, if the building doesn't need more than that for level 13.
My main complaint with this event is that the number of quests that involve producing 50 - 70 simple tools or whatever are excessive. I would much rather they had kept with the new concept they tried in a previous event to include quests to visit neighbors and changed a few of these click intensive productions to "visit 20" (or more) neighbors instead.
I'm also not crazy about having 2 different sets in one Event. I have to keep going back and checking GoK to see if the set building is for the set I'm actually interested in making.
Most of my cities are far enough along that having a set that's mainly T1 goods is pretty useless to me. On the other hand, on my second smaller account which I set up as a training example for my Arendyll Fellowship, (and also have a small city in Winyandor since that was where they put me first on the second account and which I'm still playing because I'd hate to add to the dead cities there... half of my "neighbors" are now uninhabited coin cities!!!
) I really like the Harvest set because in Winyandor, I'm always short of Tier 1 goods.
Now as to the question "Can you get all 3 main buildings without diamonds?" obviously it's too soon for me to tell but in at least 3 of my 9 cities I've already collected the first 2 prizes and I have 50 to 150 points towards the third with double days still to come. I'm sure that, if my luck holds, I will be able to get the 3rd main prize without diamonds in at least one of those cities. (One of the 3 is my tiny training town, btw... ) My luck was certainly holding in my tiny Winyandor town today when I went for the Temple Entrance... took me about 5 tries to get it and the first 4 tries were all extra moon splinters, some of them the 200 extra, so I ended up with more moon splinters that I started with and got the Temple Entrance! Now that's the kind of luck I like to have!