graphic design is a must, but a good understanding of photography, journalism (including editing- being able to sub an article down from 100 to 600 words to make it fit on a page) would also be useful, so excellent english skills would help.
art in general is ok- if you are developing a good visual language and understanding of composition, and perhaps some art history.
if you really want to get ahead, start designing your own websites, or for friends- this will teach you not only abuot working in the real world, btu how to work with others and negotiate- as an AD you'd have a team under you, so youd have to be able to get along with other people.
you cant just waltz into an AD job- you have to work your way up through the ranks- starting as a juniour.

i went to st martins and did graphics; platon, a well known photogrpher came in to lecture, and said taht while he was there the photography dept was downsized for a while, so he ended up setting up shoots in the corridors, ahlls etc,a nd said it proved oddly useful. it ment it got to be really self reliant, work fast, and know lighting inside out.
you need to have those kind of skills too- ADs have to be quick, reliable, single minded, and have a definate vision; its nothing like it is on ugly betty!
work experiance is generally a waste of time, as you get photocopying and tea making- not much else.
even getting into a juniour's position can be hard, so you'll need to stand out from other applicants- seriously find something you enjoy and make a website for it; it'll show emplyeers that you are really passionate about design, and can think for your self, and are reliable.
, or sign up to some graphics freelance sites, and offer yourself for free. its what lots of people do- you get to build up a decent portfolio of real work that way.
sayinf 'i did a 3 week course in photography' means nothing; showing them you established your own website with a special theme shows you're inteligent and resourceful- take a look at the sartorialist site for an easy thing to do- but try making it about old people, or people with heavy shopping bags, or smoking outside of office or something...

thesartorialist.blogspot.com

street style is a bit overdone, but this guy hasa great eye, not to mentioned a super camera; you dont need the latter, but you do need to demonstate the former.
photography is as much about editing etc as being an AD on a mag; its all choices and deadlines.