The Airport Express (AEX) is a wireless network link designed for audio use.
I am making some assumptions here, firstly that your iThing is Airplay capable, ie an iPod touch or some type of iPhone and secondly that you have a computer network.
If you have, then the AEX is connected to your network and once set up, recieves music wirelessly over Airplay. It has a decent digital to analogue converter onboad and outputs regular two channel stereo from a jack similar to a headphone jack. All music selection and control is done from the iThing.
This output can be plugged into a regular amplifier/reciever which in turn drives a pair of speakers, but given the tight budget you will get better value combining the amplifier and speakers together to get powered or better, active speakers.
The cble needed will be a mini jack to two phonos, about 2-3 meters and splitable to give a stereo spread. Almost any proper speaker stand, around 20-24 inches high will do, getting them well sighted and rigid is the important bit.
Prices vary depending on the market but in the uk, a setup comprising an AEX, Presonus Eris 5, stands and cables can be had for around £350. Ie...
http://www.apple.com/uk/shop/product/FC414B/A/airport-express-base-station
http://www.andertons.co.uk/active-monitors/pid29608/cid738/presonus-eris-e5-active-studio-monitor-single.asp
https://www.audiovisualonline.co.uk/product/16052/mission-stancette-silver-speaker-stands-pair/
https://www.audiovisualonline.co.uk/product/3613/qed-profile-3-5mm-jack-to-phono-cable-1m/
BTW. If you have a non network capable iPod, then you can use the cable plugged into the ipod itself, forgetting about the AEX. You will be teathered by a cable to the speakers, not ideal.