Hi Welcome to the DJU Forum
Choosing gear depends on exactly what area of D.J'ing you wish to get into?. If you want to do the general Mobile D.J work (Family parties - Weddings, 21st Birthdays etc) then the equiment you require will be different to what you would need if you want to be a mixing / beat matching D.J or eventually want to get into the club circuit.
If you are looking to practice at home, or cover very small house parties, then you can easily set yourself up with the basics for under $1000. Which would buy you something like a Gemini Kit consisting of Turntables, Mixer and small amplified loudspeakers.
Another choice to make, is whether you want to use CD or Vinyl - many club D.J's tend to use a mixture of both types - or at least can mix using both types

where as the majority of Mobile D.J's use CD material for practicality.
If you do want to cover large venues or Do Mobile work, then you will need more equipment, and obviously the amount you need to spend will increase as well. Typically, if you intend to do mobile work then you will need to consider purchasing the following:-
Dual Cd Player (or 2x Turntables)
Reasonable Quality Mixer with at least 2 audio channels (inputs) and 1 Mic Input
Stereo Amplifier (Rated at least 250 - 500 Watts Per channel)
Pair of loudspeakers to suit your choice of amplifier
Microphone
A few basic lighting effects
A good selection of CD's (or vinyl) that will appeal to all age groups
If you intend to do mobile work, then you will find lots of discussions an the best Amplifiers and Speakers etc around the forum
If you just want a system to mix with or practice on at home then you may find some useful information
HEREYou may also find the "Crooksey's Corner" section of interest to you, since there is also some links to suppliers of Disco Equipment in the U.S