Another tip from someone Buy 4 or 5 extra transom plugs. Put one in the boats glove box, your tackle box, truck glove box, buddies truck glove box, etc. Also, a first aid kit should be high on your list. Outboard motor support for trailering keeps the motor from bouncing on the transom. Also, a second trailer jack on the back of the trailer is very handy for storage to keep from getting flat spots on the tires or even changing a tire. Check the size of the bilge pump, if it is on the small side or at max rated capacity for the boat get a bigger one. Don't forget fire extinguisher too.
Locking chains for the trailer safety chains and spare are nice if using public ramps. Same goes for keyed lug nuts. Don't discount dock lines and fenders, also a line suitable for towing or being towed, preferably polypropylene so it floats.

