Answering your question with a question -- which victory condition are you pursuing?
I agree with
@Tiberiu post about using a single food-rich city to be a food producer that exports food to the rest of your empire, and thus all cities grow. Let's follow that logic further, to see what several larger cities could do.
For Domination, one could set a number of cities to Economic Development (energy), and buy an army in mid-game. That is between turns 100 and 150, after you have several cities planted. Success would depend on whether you need only a navy, or both an army and navy/
For Contact, setting several cities to energy could get you the 1000 energy you need to ignite the Beacon quickly. But in all my Contact victories, I've been able to crank up my energy production (as another faction, not Al Falah) so that I have 1000 in the bank by the time my Beacon is finished construction.
I'm not sure that Al Falah's trait is especially suited to Promised Land victories. Energy is collected from all cities, so setting some cities to energy might let one buy units to push through the Emancipation Gate. For Harmony, one can buy Xeno Sanctuaries with energy, but not Mind Stems; the latter need to be built using production.
For all of the affinity victories, trade routes sending production to the build city helps speed construction of the final wonder. A bigger city (grown by sending it food from Ag Development towns) would build the wonder faster.
Setting smaller cities to Science Development might give a boost for Harmony, getting all 3 techs researched earlier.
After getting the Might policy for faster affinity accumulation, a Science sprint might make sense.
To answer the original question, it seems that production buildings and trade depots would be useful for Al Falah. Colonists, too, since one would be pursuing a wide strategy with more than 5 self-founded cities. Depending on how close your neighbors are -- and how belligerent -- building units will also be needed.
I've read comments from skillful Civ3 and Civ4 players who write that most buildings are not needed; they build a lot of units and go to war. I haven't read enough strategy articles to know if that applies to Civ5 also; the warmonger diplomatic penalties are pretty severe. The faction leaders in BERT seem a lot less bothered by warmongering. In all of my recent games, the AI have no reservations about DOWing each other, more frequently as the game goes on.
Independent of which sponsor I'm playing, I tend to build a LOT of buildings, especially health buildings.