Banks, Training Grounds and Hospitals are the only three buildings within the city walls that you can have multiple times. All three of them have specific benefits and you should be aware of these when choosing for a certain setup.
Banks give a one percent training speed boost for every bank, every level, with an additional 4% if you upgrade a bank to level 21, so the total training speed boost of a Lvl 21 Bank is 25%. Since at this stage there are limited other ways to increase training speed, the Banks are a very important way to do so.
Training Grounds increase the troop training queue, the amount of troops you can train at the same time, they do not (!) directly influence the training speed. In addition Training Grounds give a Troop Defense boost, 1% at levels 5, 10, 15 and 20 and an additional 6 for a total of 10% at level 21. For the Training Queue I always like to aim for a situation in which I can train Tier 3 troops with 3 Day Speed Ups once my buildings are upgraded to level 21. 3 Day Speed Ups are economically the best to use for training (smaller speed ups cost more per day).
Hospitals increase the capacity for troops that are not killed but hospitalized when your base is attacked. In additional Hospitals give a 5% Troop Health boost at level 21.
If you are a trap account, you likely will need lots of hospitals, the choice is simple. If you are mostly attacking, not really training much anymore and either nobody is stupid enough to attack you or you always stay shielded, banks and hospitals might not be of much use, in that case you might opt for relatively many Training Grounds for their Troop Defense boosts, which limits the number of your troops that are killed when you are attacking.
Although it is not as easy as resetting your Commander Skill Points it is good to realize the building configuration does not have to be permanent. You might consider having more banks early on in the game, when you are speed training lots of troops, while later on you replace these with either hospitals or training grounds depending on whether you are a trap or attacker/rally leader.
Each building has its use and in most cases is a prerequisite for other building upgrades as well, but it is good to think about when you will need those buildings and whether it might be good to wait with building them or tear them down, to make space for extra Banks, Training Grounds or Hospitals.
One example is the Warehouse. Once you grow larger the benefit of having a Warehouse is negligible, whether or not you still have 2m resources of each is the least of your worries when you have been zeroed and will likely only be a tiny drop in a bucket of the resources you need to retrain and heal your army. The warehouse is however a prerequisite for 3 Headquarter upgrades and one of the many requirements for Research Facility level 21. Not building it is not an option, but tearing it down the moment you have completed Research Facility Level 21 to replace it with something more useful is what most players do.
Another example is that you might want to decide whether you really need the Prison and Death Row early on in the game. If you do not use fake rallies as a method of defending yourself, you might even wait with building the War Room and Embassy for a while. Eventually you need them, but even having just 4 level 15 Banks instead for a while gives you a nice extra 60% Troop Training Speed boost.
Best is to consider above tips and apply them to your own situation, and only see below setup example as what it is, an example, not something to follow blindly.
If you start out with 3 Training Grounds, 1 Hospital and the rest Banks (even considering not to have Embassy, War Room, Prison and Death Row early on in the game) you benefit from a large Training Speed Boost (of course don’t forget to set your Commander Skill Points each time you start a speed training session). 3 Training Grounds at level 21, together with part of the new economy Gear to increase Troop Queue, will make sure you can get to a situation in which you can speed train tier 3 troops with 3 Day Speed ups. Depending on the type of account you are, once you feel you have done most of the speed training you want to do and you want to start focusing on your core activity (e.g. rally leader, trap account) you can replace some of the Banks with Training Grounds are Hospitals.
Think about what type of account you will be and realize you do not need all buildings all the time, and that in general your best setup might also change over time as your account develops further and your focus evolves.
Contributed by: GamesGuide on April 12, 2016