Now that Beginner Protection is drawing to a close, people are asking what level buildings they should aim for. These are the minimums, and ordered in the level of importance. Please note that you can still build beyond these levels, but I recommend until BP wears off, putting any resources beyond this straight into AT production.
BUILDINGS:
Needed in ALL cities...
Archer Towers: 1,000
Walls: 4 (level 5 or 6 would be better)
Beacon Tower: 5
Embassy: 3
Town Hall: 4
Cottages: 10 or 11 built at level 5
Resource Fields: 6 or 7
Academy: 4
Rally Spot: 3
Barracks: 9 or 10 built at level 4
Suggestions for other buildings (not requirements):
Marketplace: 2
Relief Station: 2
Feasting Hall: 3
Inn: 4
RESEARCH:
Again, in level of importance
Archery: 6
Informatics: 5
Lumbering: 6
Masonry: 5
Mining: 4
Compass: 3
Agriculture: 4