I do many events that are a full day driving distance.
The bigger items I usually bring:
1)Boom
2)Spin. Pole
3)Tiller crossbar
4)Rudder
5)Daggerboard
6)I brought a spare Mast extrusion to FL, but that's because I have one, I wouldn't buy it.
7)Rudder castings if sailing in surf
Gudgeons if sailing in surf9)Tiller extension
Smaller items I have at every regatta:
1)Gudgeons
2)Rudder pins
3)Rudder cams
4)Spare spin halyard
5)Misc. lengths of line, small for control lines.
6)Pins and ring dings
7)Shackles
Harken blocks (such as spin halyard block)9)Rip Stop Tape
10)Battens, especially the upper ones
11)Stopper balls or figure eight stoppers for trapeze
12)Spare Dogbones (usually carry one of 10 & 11 on boat with spare line)
13)Drain plugs
I've probably forgot some stuff but that's a good start.