My first recommendation would be - run as many ethernet cables as you can.
WiFi is necessarily half-duplex in operation, so every time you have to
re-transmit a packet, you're halving[1] your data rate. Add a few
repeaters, and things can end up at a crawl...
Of course, cables aren't always possible, but the more you have, the less
you have to run repeaters.
Vic.
[1] It's actually not even as good as that; there is a switching time
between TX and RX. For small packets- such as are often used in gaming -
the switch time can be significant compared to the packet transmission
time.
