I picked up a metric socket set and a set of small combo ends wrenches. Made sure I had socket and breaker bar for wheel studs. Most trail repairs are going to be 10mm and smaller besides the wheel nuts. A good set of screwdrivers especially phillips type in a variety of sizes. A couple pair of pliers of various types. I carry a small bag with pliers, screwdrivers, electrical tape, spare fuses, spare Eclips for shift linkage, wire strippers, a few wire connectors, just items for any on trail electrical repair. I am sure each person will have there own ideas of what should be carried and only getting out and experiencing on trail issues will help to know what is really needed.
One thing I forgot to mention was the wrenches need to adjust the tie rods ( toe in/out) I run run into toe in/out issues after really rough and rugged trail conditions. Only takes a few minutes to "eyeball" the alignment some where close to finnish the ride. Fortunately these machines are well built so that trail repairs have been few and far between.