Sue and Henry. Defining what we carry in the tow vehicle is easy, defining the essential stuff more difficult.
Tow vehicle we typically don't carry stuff for the trailer. We carry stuff primarily for driving or exploring. We each have a rain jacket, sweater or pullover, watch caps, hats, scarf, and gloves to handle variable weather. We have two walking sticks, a loaded waist backpack for hikes and geocaching, and a small blanket. We always have a case of water in the car for emergencies, some times we're far out in dry areas. We carry two aluminum chairs, a small compressor, tire repair kit, minor tools, a bottle jack. We have a jump starter, thicker than a cell phone but about the same size. We have a snack box with nuts, twizzlers and dots for use while we're driving - 9 AM is Twizzler time. Ginny has two large print maps and usually state maps for every state we plan to be in and a magnifying glass. Ginny's a flashlight nut, never too many and she always has some. We also have a shoe box of medical supplies, actually there's a shoe box under all six seats of different types, snacks, tools, maps, CDs, first aid....
I really stuck on essentials. Of course it's Ginny but out side of that I would say the phone, it must do 20 tasks..keep us in touch, handle finances, keeps track of expenses, takes pictures, keeps notes, serves as an ebook, gps, geocaching tool, flash light
, night clock, campground directory, entertainment finder, restaurant guide, tracking device on hikes, auto locator, timer for planks, ....
Next I would suggest our Verizon hotspot. It makes the phone, TV and computer work. We switched to Internet TV last year, giving up out Sat Dish.
I did ask Ginny this question and she said the bathroom in the middle of the night. I do like front couch, I sit there at night working on my computer.
Of my modifications I like the 3 rear bumper storage locations and the 5 under the floor storage locations, they all keep dirty and needed but rarely used items out of the trailer. In side the trailer I like all the defined storage locations, particularly the added drawers and overhead cabinets. Nothing is piled in, one drawer for underwear and socks, one for shorts, one for Tshirts, a place for jeans and..... You can see most of them in the following long thread. Every year I add something to make it a little better.
Preparing a 1991 Scamp 16
Sorry I don't do well on essentials. Not to be too esoteric, but what's essential is the freedom, time and mental and physical healthy environment of living in out limited 92 square feet and the virtual infinite space of North America.