Light can be cast on any weapon... not just the weapon you actually use
[Linked Image from gog.com]

so i carry a spare staff [its big and its not heavy] but as a barbarian you probably want a javelin

like a candle you can move this item around the floor as a free action... picking it up/ [equip or throw counts as actions or bonus]

i suggest a Javelin because you can throw it at the spider [hit or miss] it will then be placed on the map at the spiders feet so you did a little damage lite it up + unlike a candle it doesn't blow up when that spider puts a web spell down

not the best spell but imo worth playing around with... anyway hope thats cleared things up

Luke Skywalker: I don't, I don't believe it.
Yoda: That is why you failed.