Before you spend wodges of cash
smartphone time download the app WIFI Analyzer by farproc
Start simple and look at what is using the 2.5ghz range, then the 5.0ghz range
Most routers are factory set to use channel 9. i bet if you have a look there will be at least 3 or 4 neighbourly routers
using the same channel(frequency) ... the more on the frequency, the more congested it becomes.
Techy time ... once you identify what channel has the least use you need to go into your router settings,
and find the wifi settings, then specify a fixed channel that you want for your network say 2 or 3 --- it all depends on your router ...
Good ones go up to channel 14, normal run of the mill stuff is 12 or 13
however you need to have equipment that will also accept channel 14
Once you have changed your channel, log off all the stuff thats currently using wifi and get it to reconnect,
it will automatically conect to the new(your) channel and - lower congestion
A couple of other thing to check in your router settings ..
make sure your transmitting on 2.5g or 5.0g only, dont have a simultanious 2.5&5.0 transmission
Also check your lowest group for conection
you want to be running at 802.11n or 802.11ac if your on 802.11g then everything runs to match the lowest speed
g is 54mbps n is 600mbps ac is 1300mbps
If you do the same for the 5.0 band, your more than likley find sod all on there
if your equipment supports it use it
Also move your router --- no good having it downstairs by the phone socket
the wifi coverage is best described as a ring donunt with the router at the centre so lots of coverage on the level of the router,
but will tail off the further away, above or below.. (-)
my router is wall mounted at ceiling height onthe stairs (I) it spreads through the house longways and the width spread is fine