Preparing to purchase my first AR 15. IWI Zion top of the list...what do you guys keep stock?

Soon to be first time AR 15 owner. IWI top of my list. From research, seems most people do many changes/upgrades to their ARs. I'm looking to do some that make sense for me practically and budget wise. Say, $2K tops budget included the Zion 16in which I'm seeing 700 to 800 right now. So let's say I have 1.2K for changes and upgrades. What are some recommendations? Use will be primarily for training, range fun and home defense. I understand the strong opinions out there for a 14.5 or smaller for home defense. Still going with the 16. A goal is to be able to hit targets 100 yards out consistently. When I get to that point I'll consider going gucci on further upgrades or a whole new build from scratch.

What have you guys kept stock? And what would you upgrade with a 1.2K budget for the needs I mentioned? Thanks.