In the past I have had success with simple & cheap DIY parabolic reflectors

http://blog-on-wifi.blogspot.com/2011/11/deep-dish-cylindrical-parabolic.html

and “Pringles Can Antennas” (Google it)
to extend WiFi range in a “rifle shot” direction.

I have also used 30 gallon galvanized steel garbage cans
to boost 800 Mhz band cell phone signals very similar to pringles can method.
The cell antenna needs to be about 4.5 inches from the bottom of the 30 gallon garbage pail.

The “coaxial multi-dipole” WiFi antennas
like the D-Link model number ANT24-0700
boost signal in a 360 degree circle by redirecting the signal “wasted” in the up and down directions.