Buildings: Tavern-Museum(?)-Town Hall
What you want to do after you complete the GR level's is get the population sky high. To do this, upgrade the tavern twice, then upgrade the town hall.
By filling up the order in the tavern, you can get a lot of happiness, which is a lot of population
The museum, if you have it, will do a lot for you too
the goal of exploding a town is to get a good population; the more population, the more tax payers, the more resource gatherers, the bigger your economy is. It will help that town be more self sufficient later on.
