Gap insurance covers the difference if your car is totaled and you owe more on your loan than your vehicle is worth.
If you’d like to do the math for safe measure, you can calculate the depreciated value of your vehicle after a year (it will likely be worth 10-20% less than its purchase price) and your anticipated loan balance after a year of making payments. If your math indicates that your loan balance may eventually exceed the car’s ACV, you should buy gap insurance at that point.
Most insurance carriers offer some form of gap insurance, so you may be able to add it to your current policy. And if you decide you no longer need it, you can easily remove it.