My theory is the more you take the more likely that the car will have problems dragging aroung a boot load of ballast.
Take some wire (coat hanger style) and pliers, if you need to fix exhaust mounts on the way it is handy to have some wire (you can usually find wire on a farmers fence but they get annoyed if the sheep get out)
I just did a big road trip in my wifes Ford Telstar (1988 2.2 auto, it was free when I worked at a wrecker) I took oil, water, coolant, brake fluid, degreaser, silicone spray, windscreen cleaner, WD40, washer additive, plumbers tape, cloth duct tape, insulation tape, thin tie wire, thick tie wire, metric tools, screwdrivers, a file, rope, paper towel, hand cleaner, rags, etc.
I only used half a litre of oil and the windscreen cleaner and rags.
I'll echo the money, I have an old taxi coin dispenser full at all times good for tolls and stuff 