I've looked up the rules and such for IDPA, as well as the brief description on the sticky on this site, but they don't really tell me what normally is used in IDPA, or what setups people normally go with.
I shoot an M&P Pro 9mm with a Dawson Precision fiber optic front sight, APEX aftermarket trigger parts, from a Blade Tech DOH Holster (DO part removed). It's about as fancy as you can get and still be shooting in SSP.
I've also shot with a compact Glock 19 from a homemade IWB holster with a single spare mag in my pocket.
People will run a wide variety of equipment depending on their goals. Do you want to win, or do you want to just have fun, or practice with your everyday carry gear?
Each is fun and challenging in a different way, and none is better or more "IDPA" than the other.
Sloppy nylon holsters or unsafe handling aside, as long as your gear is functional and safe, shoot it however and with whatever you want. You're not going to win the first match, and no one is going to send you home from your first match for having equipment that technically breaks a rule.
Then just go shoot, tell them you're new and want some guidance, listen, be safe, help paste targets and clean up.
After the match, read the rulebook and see if the rules make sense now that you have some context. After a while it gets tiresome learning the rulebook one penalty at a time