Welcome fellow flyer you have just entered into what I believe will be something that will blow away, exhilarate & totally fascinate you
In order I think I bought:
Snap on off prop guards bestem aerial I got, as you grow in confidence ditch them
Case, got my bird when it first came out & they were looking for crazy money ended up buying from China for about $40 & does the job fine ( 1 month delivery )
1 ft short cable for RC to device
Aftermarket gimbal guard
Set of ND filters for video in my case Polar Pro 2nd edition
A external hard drive I got a Seagate 4TB cuz video gobbles up space
A lanyard for your RC cuz it's worth a few bucks & brill if you hand catch
Aluminium windsurfer for when you are in the mood to go that extra mile ( location depending we love our hobby )
Next I think I'll get a anemometer have being relying on my weeping willow which in bang on accurate but it's only $10
Wish List MEGA : 87" 4k curved UHD TV setup don't care if it smart as long as it plays 4K
A bad *** 4K laptop
& defo the P4
Have fun & keep it
Have loads of fun & enjoy