I want to preface my remark with the fact that I am currently the "acting" IT manager for an engineering lab (in addition to being a functional engineer), which was recently purchased by a large corporation. I have seen our business grow from 7 people to 35 and finally to 700 folks as part of a new corporate division - I still manage all of it. I am told that I have done a good job and made sound decisions in terms of network equipment selection and overall system architecture. I'll admit that I can definitely still be a bit of a *******, but hopefully some of my experience will help someone here.
Of course, when the building size is small and the number of users are as well, often times a single quality router with good Wifi (dual radio 2.4 and 5 GHz) will do. However, as the building size and population increases, the next step is to consider high powered access points with PoE cable runs to strategic locations. When this is not possible, a mesh router system could be a solution and the best one I have had experience with is from Ubiquiti Networks. Any larger and you'll need to get into commercial/enterprise systems which includes high power dish transmitter/receivers between large air gaps/buildings or just run cable.
As far as the Ubiquiti parts go, the company recently designed a system aimed at the consumer/residential segment. A solid choice for many is their Amplifi HD product, which can be had in a kit with 2 mesh point devices in addition to their router. I believe that system used to be obtainable for around $200, but I'm sure the price has gone up. For a significant boost in throughput and performance, they released the Amplifi Alien system which boasts additional multi-band radios and can theoretically achieve 4x the performance of the Amplifi HD system, which is already very good, but you'll pay for it. Beyond that you will start to get into their enterprise class products, starting with the Dream Machine and UniFi series parts, but the cost starts to really get into another league altogether.
In any case, nothing comes close to the refinement in execution that exists in the Ubiquiti user interfaces. They are genuinely plug and play systems, even at their enterprise level - simple to install and configure, which is clearly one of their engineering team's top design goals. In over 10 years of using Ubiquiti components, we have had zero issues in both enterprise and residential environments.
