Ok my lists are usually pretty indepth for work, but this is for normal day use so I'll keep this short and cheap:
Waterproof pouch:
-photocopy of drivers license, insurance papers, emergency contacts.
-Detailed map of local area and larger areas.
-silva compass
-GPS with mapping loaded and important features if traveling rural area
-$100-1000 cash
Vehicle Breakdown kit. The actual tools you would add in as well as this list will depend on your own skill with a vehicle.
-Spare fuel
-Jack, the ones with car are usually shit so i recommend buying a better quality version
-Consider air jack- can be used to roll vehicles over.
-Basic tool set
-wood block (for vehicle changes on soft ground)
-tarp
-air compressor
-Spare fuses and bulbs for vehicle
-tow rope
-winch
-triangle warning signs
-reflective shirt
-shovel
-fire extinguisher
-dry rags
-mechanic gloves
-wd40
Comms
-pair of radios charged and spare batteries
-spare pay as you go cell phone
Bag with internal waterproof bag (canoe bag) to contain:
-rain jacket, warm clothing, boots, socks, underwear, gloves, hat for hot/cold weather
-headtorch, flashlight, spare batteries waterproofed
-fire lighting kit- so many ways to choose, but at the least lighters waterproofed
-paracord
-duct tape
-space blanket
-emergency snacks taped up so you dont eat them you greedy slut
-whistle
-bungee cords
-jump cables
-Spare water loaded into canteens as well as a large container
-fixed blade knife/pocket knife/hatchet/hand saw
-roll mat and sleeping system
-towel
-trauma shears
Other considerations:
-Handbook for most popular other language, Spanish I'd guess in this case
-Know where nearest trauma rated hospital is located and expected time/distance
There aren't many medpacks I'd recommend 'off the shelf', they are often overpriced and full of fluff. It would have its own list I could do if anyone wanted (I'm a paramedic too).
This could be a very in depth list...but right here are the basics. At work this stuff was a daily check, at home I'd check this all once a month for damage and practice using it, as well as checking battery levels etc.
Also highly important that all of this equipment is tied/bolted down, the last thing you want is debris flying around the vehicle to fuck you up with in a car crash. I have my breakdown kit in a box and my backpack carabinered to the back of the vehicle beside it. Fire extinguisher should be in the front cab with you but screwed in/secured somewhere near you.