1. Look for event buildings that have population, this frees up a lot of space in the long term & gives FPS / Combat from most of them.
2. Update your houses as you go up ages (you can overwrite one age building with another by building on top of it)
3. Tower of Babel GB gives population (not a great GB, but can be useful at lower levels).
4. The Lords Manor is a good interim building 4x4 with a population of 130 as a start in BA gold and FPs when motivated. look for it in the AD
Eventually you reach a point where the event buildings are providing all the population and happiness you will ever need, and you will no longer have population specific buildings