Fill your black water and gray water tanks with clean fresh water then empty them through the "slinky" hose to check for leaks
. Better to get wet with fresh water than waste water in the event of a bad slinky.
Get a bottle of "Odorlos" black water tank treatment.
Take along a one of those grille lighter stick things for the stove and the water heater.
Don't use the shower without a curtain.
You might consider a fresh water shore water filter ($17 @ Walmart)I use one to protect the trailer and keep the system clean.
A flare/reflector kit.
A brake spoon might be handy ,if you have the skill for it's use.
A small tool kit with a multi screwdriver, pliers, adjustable wrench, a small tarp, A lug wrench and jack (sometimes the tow vehicle's will fit)
duct tape,electrical tape, A length of 3/16ths nylon rope, a tire pressure guage.How about a small First-Aid Kit?
It is important to watch the curbs and angles of approach to driveways and parking lots... take it slow on these until you are able to judge them, to prevent damage.
Don't forget bedding, towels, washrags pillows , along with cooking and dining utensils.
AND,Last for now... Toilet paper. we like to use a container like the one in the photo,remove the core and dispense from the center, this allows you to keep it both dry and handy in the bathroom...