Okay, let's just assume that you have chosen a handgun suitable for self-defense (another topic altogether) and you can LEGALLY carry it with you to your place of worship.
What's an acceptable MINIMUM proficiency test with a handgun? Try this: 5 rounds fired into a 5 inch target at 5 yards in 5 seconds. When you can routinely and consistently do that from a low ready position, then work on the same drill drawing from a holster worn under a covering jacket.
Remember, you MUST practice as frequently as possible so that you aren't a liability to both yourself AND your church.