Originally Posted by
whitecat
Cotton is cheap, and unsuitable for this purpose. We're not in the previous century anymore, synthetics are much improved these days, take a look at technical materials such as Coolmax...
...such clothes can be had for cheap today, if you shop around
The OP is on a budget. Based on what she says, she doesn't want to be shopping around. She doesn't want to be shopping at all!
Originally Posted by
weepingwillow
...money is very tight (hence the incentive to ride my bike to work) so I cannot go crazy buying a bunch of gear / clothes right now.
Cotton is perfectly suitable for a 13 mile commute. Heck, I've used it on century rides with no problems at all. But anyway, the OP is not doing a century ride every day, rain or shine, at 30mph. She's doing an hour's ride once a week (presumably when weather is good) at around 13mph.
Getting her on the bike is key. Getting her to waste time she could be cycling buying accessories is counterproductive.