I'd try them on in a store first; that way you have an idea of how they fit.
Are you wearing them to classes? Three pair should be fine for that. I have a lot more (of course I am a girl and work in peds, so there's a lot of fun stuff out there

). But, a general rule is to have a week's worth plus an extra pair in case you don't get the laundry done. OK, maybe that's not a
general rule, but it should be

.
Have fun; I remember how excited I was to get my first pair of scrubs


.