I would suggest a USB card that has the ability to replace the antenna. You could also use a bridge type of device but it may put you over your price limit.
Almost every device you will find on the market will transmit at the maximum power so all will have very similar range. The only way to increase range is to use directional antenna.
So first thing is to place the USB device on a 15ft USB extension cable and place it near a window. If it is small enough you may be able to put it outside unobserved. If this is not good enough get a directional antenna and directly attach the USB to the back of it. You want to avoid using any microwave coax if you can since that just absorbs signal. Since most antenna use N and most consumer wireless users r-smc connectors you will need a small adapter , normally the places that sell antenna sell these also.
Even directional antenna may not help if too much of the signal is being absorbed, many times you need antenna on both ends to make this work