most important part is a fresh set of clothes, and a shower
i used to cycle 10 miles to and from school every day with a 20 pound bookcase
nothing but jeans, some warm sweater , and a waterproof jacket if it rained, perhaps gloves if it was really, really cold ( lower then 5 C is considered really cold here

)
and no fresh clothes or shower in school either
oh yeah, and it was uphill in the morning, and uphill going back too
and my chain was made from paperclips, coz we wuz poor