I haven't worked in housekeeping, but I pass by and chat with several daily! I love them!!!
You will be issued unforms (I'm sure you have to pay for a portion . . ?? as it's not the department I work in). There are day and evening and sometimes 'theme' uniforms. They do have shoes onboard to puchase, but if you're particular, get a pair of comforable, full black low heels shoes. All black, no markings. I've never seen a female cabin steward wear a dress or skirt - so perhaps just enough socks to get you through a week. And don't go too crazy on personal clothing - all you need is a couple of outfits to go out in ports or to 'kick back' in the crew bar. You'll be in uniform all other times.
And I'm sure you'll be in training for at least a cruise or so - there's a strict 'way' of setting up a cabin, and at least two weeks or so of general ship training you'll be doing. (marine, safety, corporate orientation). By then you'll know how many cabins
I thought of something . . . go to webshots.com and type in 'room steward' into the search bar. Lots of photos of stewards come up (though not too many ladies), but you'll see in general what a unifrom looks like. And you'll see lots of those towel animals you'll be learning to make