If the person you are buying a gift for doesn't already own a drone, then I would consider getting them a bundle which consist of the drone and most of the accessories they will need to get started. This is probably the best bundle you will find on Amazon; DJI Phantom 4 Quadcopter Kit Bundle with 4K Camera Gimbal, 3 DJI Batteries and Accessories (11 Items)
If the person you are buying for already owns the DJI Phantom 4, then these are some of the accessories I would recommend buying for them.
Phantom 4 battery; $97.20 - http://amzn.to/2eVUoHk
Phantom 4 camera lens hood; $7.99 - https://goo.gl/KL2TGQ
Phantom 4 Battery Charging hub; $21.98 - http://amzn.to/2fixrg0
Phantom 4 Propeller Guards; $19.00 - http://amzn.to/2fiC1ee
Phantom 3 / 4 Remote Control Laynard; $7.99 - https://goo.gl/OqtuK2
Phantom 4 Lens Cover; $19.99 - https://goo.gl/Zh9FaL
Skyreat Parabolic Antenna Range Boosters; $16.99 - http://amzn.to/2fJr723
Review of these boosters (http://www.crizzo.net/2016/06/skyreatparabolicantennaboosters.html)
Phantom 4 Quick Release Propeller [2-pack]; $19.99 - http://amzn.to/2gzVCtb
Phantom 4 Monitor Hood; $14.99 - http://amzn.to/2g8turX
Review of this Product (http://www.crizzo.net/2016/04/i-recently-purchased-topbest-sun-visor.html)
Phantom 3 or 4 ProCrafts Cases backpack; $139.99 - http://amzn.to/1QSkVvE
Review of this backpak (http://www.crizzo.net/2016/05/procraft-cases.html)
Phantom 4 12-inch Lightning cable for iPhone; $13.99 - http://amzn.to/2btE9gY
Review of cable (http://www.crizzo.net/2016/08/cambondlightningcable.html)
Belkin USB-A to USB-C; $23 - http://amzn.to/2bv4qJe
Review of cable (http://www.crizzo.net/2016/08/belkin-usb-c-cable.html)
Polar Pro ND Filters for Phantom 3 and Phantom 4; $49.99 - http://amzn.to/1YSMquI
Review of filters (http://www.crizzo.net/2016/04/nd-filters.html)
SanDisk 64GB microUSB card; $19.99 - http://amzn.to/2gzUzIT
Here is a post I wrote about 5 accessories you should buy with your DJI Phantom 4, if the person you are buying a drone accessory for doesn't own these, this is a great list you might want to consider; http://www.crizzo.net/2016/04/Phantom-4-must-haves.html.
If you have any questions or comments about any of these products, or you need help with something drone related, feel free to leave a comment and I will do my best to answer your question!