Man... how long is a piece of string? You could ask 30 people and get 30 different answers. So... rather than suggest what you SHOULD carry, I'll simply tell you what I do carry and let you decide for yourself. This is an abbreviated list... you really DON'T want to carry all the crap I do.
-Metric socket set with at least 8mm, 10mm, 12mm, 14mm, 17mm, and 19mm sockets
-Combination wrenches in the same sizes plus a couple of screwdrivers, pliers, cutters
-Hub socket, 24mm socket
-snap ring pliers
-super glue and tire patch kit
-electrical tape
-a few feet of 5/16' fuel line, vacuum line, and some clamps
-a few feet of electrical wire and a few asstd connectors/crimper
-spare belt or two depending on your setup (put on new ones, keep old ones for spares)
-a little bailing wire
-good flashlight, or better yet, a headworn lamp
-make sure whatever jack you carry is capable of getting a tire off of the ground on the trail. Bottle jacks are, IMHO, more trustworthy than a Hi-Lift and so I carry a couple of short pieces of 2x6 to use under the bottle jack when necessary.
I've probably left some stuff out, but others can fill in... that's the basics... you really don't want to know what's in the back of the Whale... hell, I'm not sure I KNOW what's in the back of the Whale!
JJJ