As far as I understand it :
You need a trigger, the cable, a controller, and amp to run it through.  A single trigger will run you $15 -50 or more depending on the quality you want. I've heard the ddrum triggers are pretty good.  The controller may be a pricey item. You probably want to shop used for this, seeing as its a simple application an old and simple controller would work fine. New ones run $200 or 300 and up (you maybe be able to find cheaper ones.  Then from there run through an amp or through house PA. 

I am fairly new to this and trying to figure out the whole trigger game too. I'm probably missing something simple so others, chime in!