I have been playing on beta so I have had this contest going on for a while. Here is what I can report:
1. Don't stress about anything taking a while on the second quest (the non episodic one). I have 13 days remaining and I am already done with all of those quests. There are only so many of them.
2. Don't open chests unless it is a reward you really really want. There is a different daily prize and they get better as the contest goes on. The early prizes aren't so great. In fact, the last prize seems to be the best one, so if you can stand it, you might want to wait before you open any chests until the last day. At least, I think it will be given on the last day. Some days the reward is only some runes. You'll want to wait for buildings at least. As people have said, the higher your chapter, the better the buildings are, so if you are close to finishing a chapter, finish it before you open a chest. Here is the list of buildings you can win. The culture numbers and pop numbers are the maximum if you are in the Orc chapter. I didn't make this list, so I can't swear it is totally accurate:
size: 1x1
Rainbow Flower Cage
117 culture and 117 Population
Spring flower Cage: 210 culture
Noble Banner: 210 Culture
Summer Flower Cage: 230 culture
Dark Signpost: 230 Culture
Heroic Banner: 250 culture
size: 1x2
Rainbow Unicorn:
195 Culture and 195 Population
Bronze Guards: 370 culture
Silver Unicorn: 390 culture
Silver Guards: 410 Culture
Crystal Unicorn: 430 Culture
size: 2x2
Leaf Codex: 700 culture
Sun Codex: 780 culture
Lava Codex: 860 culture
Observatory: 780 Culture
size: 3x3
Father Tree: 2100 culture
size: 5x3
Glossy Garden: 1760
Population and Culture
main reward:
Venars Rock I 2x4 940
Population and Culture
Venars Rock II 3x4 1400
Population and Culture
Venars Rock III 5x4 2300
Population and Culture
3. You might not be able to make it to the second Venar's rock reward unless you buy moon splinters. It takes 200 sun things to get the second building and I am pretty sure it won't be possible unless they drastically change the rewards for the daily episodic quest. I'm not even close right now. If anything changes I will update this. As I said, I still have 13 days to go.
4. Even though I am an advanced player and this does benefit me personally, I do think it is cool that you get a higher reward if you are in a higher chapter. So many of these things really harm the loyal players. Plus, even though I don't agree with anything else he said, qaccy is right that it would be very unbalanced if you got a building with that much benefit early on. If the rewards were the same, either the buildings would be crazily overpowered for lower players or crazily underpowered for advanced players. I think this was a good solution. It would be cool if they changed as you advanced, but maybe there will be more contests in the future?
5. I can't figure out why they offered the moon splinters before the contest even started. You'd think people would want to buy them after the contest has started.
6. Even though you may not get many buildings, even if you get one you can keep forever, it is something! I got lucky and won a rainbow unicorn on beta and it is my favorite building! Yeah, it was stupid of me to try for it and not wait for the glossy garden, but it is cool! Yay!
7. Obviously, you are better off opening the gold chests and having a 25% chance of getting the daily building (or two or 3 of them) vs a 7% chance of getting one of them even if you can open more bronze chests.