Getting started in Optics on handguns

[Tizuia]

Hello to all,
After much deliberation and nashing of teeth and wallet, I have decided to enter the world of optics on pistols. I have shot iron sighted pistols since I started shooting. I am now the owner of a Glock 17 Gen 5 MOS.
I will be using this pistol primarily for IDPA Carry optics and personnel training.
My questions to the experts are:
1. What holsters are good and bad?
3. Options for back-up sights?
4. What optics should I avoid, what has worked and what hasn't?
5. Any "dot" specific drills?
Thanks for the info.
NOTE: I don't want this to turn into a "this vs that". Just info on what has worked and what should be avoided.

[Scott B.]

I'd look for a nice wide field of view. Top loading battery. Great battery life. Dourable. Adjustable (intensity, a real on off option, etc).

Trijicon SRO. New, big, and fixes the bottom battery loading problem the RMR 05/06 'suffer' from. But alas, won't be cheap.