I would stockpile food and clothing at work. can you skip biking on rainy days? if not the right gear is worth the money. I like rear rack trunk bags. I use fenders. I find it helpful to still protect the bottom of the rack trunk with a sheet of cardboard covered in duct tape. I got a trunk that came with a rain cover. I used a cheap hotem style shower cap over the helmet. for pants I used good quality loose fitting (not baggy) rain pants for hiking that my dad had given me but they make some nice biking pants.

I always changed at work and never worked in biking clothes