The best way would be to run a wire.
The major problem with gaming with wireless is that data packets can go missing. The fact that you have ping spikes to 250ms suggest this is what your problem is. It's just not wholly reliable. Interference from other radio sources such as other APs, a microwave, your PC or other devices can also affect how reliable your connection is.
If you can't run a wire then go for homeplugs. If you can't go homeplugs then move your wireless card/device closer to the AP and away from sources of interference. If you have captive or rear mounted antenna try using a pigtail extension to move antenna away from your PC as much as possible, without being too long to suffer drops in power.