buy plastic drop cloth, trim to fit slightly smaller than tent bottom. bring a couople of small scraps to cover picnic table seats, put gear on, etc.

get inexpensive nylon tarp, or less expensive but more bulky blue tarp, or premium silicone nylon tarp. use to hang out underneath, or even to put over tent in extreme deluges.

get a foam pad if you haven't already. in the cold times i usually bring two pads.

a candle lantern and a way to hang it in your tent is so nice in wintertime.

bring a lot of hot beverages and decaf hot drinks like instant hit cider, herbal teas for hot drinks at night.