I am wanting to start shooting in these, and I need someone that can tell me, how much is it, as well as how many rounds, and how many magazines I need in order to be able to shoot competitively.  I don't expect to be anywhere near winning, but just want to have fun.  Any help is appreciated.

TIA!

In my area (Tulsa) match fees are between $8 and $15 dollars.
Usually a local match consists of about 80-100rd of ammo.
You can only use two extra mags on your belt,so you need three.
The regular local matches aren't sticklers for the rules but if you shoot in a major match,they are.
i'd suggest finding a rig that is already IDPA legal because you will get hooked on it.
You also need to bring a concealment garment and your own eye/ear protection.
There are always plenty of seasoned shooters willing to help newbies out.
The main rules are:
1)Be safe
2)Have fun.

In the Oklahoma City area:  ipsc.okcgunclub.org/

There are several USPSA monthly matches in the area.  I shoot the one at OKC gunclub (arcadia lake) monthly and it's a nice match.  There is also one at H&H gunrange in OKC, but it's indoors and I much prefer outdoor ranges and matches.  There are 2 matches in the Tulsa area at red castle and oil capitol gun clubs.  Here's a link to the OK USPSA matches with match and contact info for each club: www.bentworks.com/oksection/

You should also look into the differences between USPSA and IDPA matches, they aren't the same thing.  Both are action pistol matches, but in general USPSA is less restrictive on rules and types of courses; IDPA tends to be very structured on exactly how everything should be done.   Some larger clubs shoot both types of matches, but most don't.  

I shoot IPSC at SCRAP (Duncan). We generally shoot 5 stages, total of 140-175 rounds. To shoot IPSC requires more $$$ than IDPA.  I shoot Limited 10. What my rig is- 1911 single stack, holster, belt, 3x 2 mag carriers(6 mags on belt), and hearing protection. I never really use all the mags, I just like to have them. Match cost is $15. All it is for me is fun too. As soon as it quits being fun, I'm done. There is also competition in Duke.
I'd say a basic starter kit in IPSC would consist of gun, 4 mags, and a holster. You can really carry your extra mags in your pocket till you figure out what you want to do. Go to a match, look around and ask questions. Good luck.