IDPA was designed from the first days to use real-world concealed carry gear. No race guns, no magnetic holsters, etc.
For equipment, you'll need:
- A safe, serviceable handgun of 9x19mm or larger caliber
- An IWB or OWB holster worn on the strong side. The holster must be of the type commonly worn for concealed carry (no drop holsters, etc.)
- Three magazines or speedloaders (few stages will ever call for 2 reloads but it's good to have a spare for malfunctions, etc).
- A cover garment (most courses of fire start from concealment)
As far as ammo goes, the qualifier is 90 rounds. Matches are usually ~100 rounds.
You can find the IDPA rulebook on line here:
http://www.idpa.com/Documents/IDPARuleBook2005.pdf
Matt