Like Transalper said - levers, spanners, tube, patches and a hand pump. You want your gear to be reliable and you dont want to be running out of CO2 in the back country with a half inflated tyre. The best thing to do though is get lots of practice - dont use the shop
You are much better to practice at home and figure things out than try and do it for the first time on the side of a gravel road.
Cheers R
"The ultimate result of shielding men from the effects of folly is to fill the world with fools." - Herbert Spencer, English Philosopher (1820-1903)
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