1) FAA Certification: If your drone is over .55 pounds and less 55 pounds, you need to be registered with the FAA. For hobyist, this is a simple form to fill out and a $5 charge. With your certification you will need to mark your drone with your FAA “UAS CERTIFICATION MARK”. This can be placed anywhere on the drones permanent structure.
To register for your drone, use this FAA website: https://registermyuas.faa.gov/
2) Extra Batteries: One of the best things a new drone pilot can purchase is an extra battery. The thrill of flying only last as long as the battery does. For micro drones, I recommend having at least 4 batteries. The micro batteries last 2-4 minutes per charge.
Race drones are in a similar boat. You get about 3 minutes on a fully charged race drone battery. For camera platforms (DJI Phantom and Mavic, Yuneec Typhoon, GoPro Karma) you get longer flight times in the 20+ minute range. I recommend having at least 2 batteries.
3) Case: You want to protect your investment and there is no better way than to put the drone in a case. There are many options for drone cases. There are hard cases that offer the best protection but come at a price of size and weight. There are also soft cases or pouches available. The soft cases do not offer the same level of protection that a hard case would but they can fit in smaller spaces and are much cheaper. There are also product specific cases for most drones.
Here are some example cases for the DJI Mavic Pro:
4) Memory Cards: The DJI Mavic Pro came with a 16GB Micro SD card. This is a great starting place but you will soon find out that 16GB is not enough storage. There are many schools of thought about the size of the SD card you should be using but here is my thinking. I use mutiple 32GB cards. Each time I fly with a new battery, I also pop in a new SD card. This would prevent me from losing all of my footage in case the drone was lost. I prefer this method over using a huge card to capture all of my footage. For most drones, you should be using a Class 10 or UHS-1 rated SD card.
5) Spare Props: Lets be honest here, we all are going to crash our drone one day. It is inevitable that something is going to happen and the drone is going to crash. The number one thing that breaks on these drones are the props. You should have at least a complete set of props on you in case of an emergency. Luckily, props are cheap and easy to replace.
While this is far from a complete list of needs, I feel that these are the required accessories that every pilot should have in their arsenal.