Before you even think about carrying a boat there are several boat trailer accessories you should have simply to assure that your boat is properly secured to the trailer. These include tie downs, such as ratcheting hook and latch tie downs that stretch across and behind your boat to make sure it stays on the trailer should any of your other security devices break.
You’ll also want some kind of winch to hoist your boat up onto the trailer out of the water. This will also lock into place to be the first form of security against the loss of your boat while traveling, which is backed up with the tie downs.
Other boat trailer accessories that are necessary are a hitch that will secure the trailer to the towing vehicle (make sure that all hitch parts are compatible so that you have easy hookup and connection), a lock for the hitch so that nothing can be stolen, and rollers onto which the boat can easily slide onto the trailer bed with no damage to the hull.