Probably the most useful thing you can do is to consider tool requirements whenever replacing any components of your bike, so it evolves into a minimum tools state.
Once that's done, you are probably best off with the appropriate selection of proper tools rather than a multitool. They will work better, and probably be as light, if not lighter. The downside is the risk of losing one and needing it later.
Tools I took on my last tour:
L-shaped bar (approx size of 7mm allen) with a screwdriver bit holder at each end, and 2,3,4,5,6,8 allen bits, flat and phillips bits, T?? torx bit, 8mm socket bit. (holder comes with Victorinox Swiss Tool, but occasionally available separately)
Park small chain tool
8 & 10mm ring spanner
hypercracker
spokey
tyre levers
small Leatherman (Juice CS4 - nothing vital, but pliers/wire cutters, corkscrew/bottle opener, scissors, knife)
Didn't take, but may be required if the worst happens:
Cone spanners
No point in BB or headset removal tools unless spares also carried
(I generally use an Alien for club /day rides, on account of it being harder to lose)