Extenders work by receiving a packet and resending it so it's a built in delay. You should look into moving the router so no extender is required or a powerline link.
For my desktop gaming computer, I currently use an ethernet cable running to a Netgear N600 wifi range extender, which is then connected to wifi. As you can probably guess, this does not provide adequate speeds as I get ping of up to ~2000-3000 ms on games such as league of legends. I was wondering if buying a pci network adapter for the desktop itself would provide more decent speeds.

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