So do I need a tactical belt to holster the gun and carry extra mags? Right now I have a simple clip on nylon holster that I have had for years just to keep it in. Or best to go and see what I need?
For IDPA you can lose the word "tactical" IDPA is geared and centers around everyday concealed carry.
You can use your clip on holster for your first match and put your magazines in your pants pocket. Shirt pocket is a no-no.
This will get you involved in your first match and from that experience you can decide what you need from what your fellow shooter are using.
The belt you choose will have to go through the belt loops of your pants.
A good sturdy gun belt for concealed carry will work. I personally use a kydex holster because I sweat real bad. Your magazine pouches must hold your magazines securely ( so they do not fall out ).
I wear 2 double magazine pouches because of sweating so bad I dare not put magazines in my pocket. You will only need 3 magazines for the match and its not a bad idea to have an extra magazine in case one of your match magazines should fail.