How do i improve my wireless aircard signal?

Well to make a long story short, my mom decided to drop our dial up connection and buy a wireless aircard… The only problem is that we live in the middle of nowhere and the signal is usually worse than our old 24k connection… I looked on the internet for “Wireless signal boosters” but the ones i found cost about 200 dollars! Sorry but my mom is very poor and couldn’t likely afford that. So is there any way that i may be able to boost the signal with some device or method?
Also if you tell me to build a antenna or something please give me a link to the instructions.