They aren't essential.I'm flying for fun and don't know if I should invest in ND filters.
Even if I'm shooting in auto mode video and still?They aren't essential.
They are used by some shooting video to reduce the shutter speed and are of no use for almost all still photography from a drone.
If you don't shoot video you don't need them.
Try shooting video without them and see if you are happy with the results.
Don't bother with them if you are shooting stills.
Try shooting video without filters first.
If you are happy with the results, there's no need to get filters.