Goodgame Empire

It's pretty hard to achieve without spending the $2. However, it can be done if you max out each quest, and submit only right before the deadline, ensuring all your screenshots will be correct. While it may cost $2, can get 5100 rubies during the 250% bonus you get sometimes while playing, the 10,000 points is around $15 in steam cards, so it kind of works out.

I did it without spending, but I know the requirement of quest 4 early, so I saved up and planned accordingly.

Did it without spending also. You just need to play the game, do the quests and dailies. Plenty of events with ruby rewards. As ManOfMadness suggested dont submit your screenies for Quests 1-3 until the last day they are due in..... gives you more time to complete Q4....
Be clear that its 15k pts here for Q4 and thats 2 thirds of any of the AAA titles from the reward store.. I personally dont have a problem grinding for those kind of rewards. In that respect this is a good quest game as its has fair effort vs reward.

Word of warning dont build the wishing well ! Its pointless as the developers no longer issue the lucky pennies needed double rubies... I wasted 2k rubies building that wishing well only to have to start all again !

Enjoy !

p.s. its 8600 rubies for Stable level 2