1 Case - those one has been great:

SYMIK A310-MA2 Waterproof Hard... https://www.amazon.com/dp/B08CKK3RMR?ref=ppx_pop_mob_ap_share

I put a microfiber cloth used to detail my car in the case to wipe the Air 2 down after a dirty landing or if it got wet.

2 64gb SD card

SanDisk 64GB Extreme microSDXC... https://www.amazon.com/dp/B07FCMBLV6?ref=ppx_pop_mob_ap_share

I don’t really use too much else. There are some 3D printed accessories on Etsy that I’ve considered. I’ve also considered a landing mat. I’ve found myself landing in slightly wet dirt and wished I had one. But, I typically land in my hand in those situations.

I got a controller adapter to use an iPad but I generally prefer my phone for simplicity as my iPad doesn’t have cellular.

There are some trick mobile apps that let you set a predetermined course, but I haven’t cared to try them yet.