To learn about sewing, I'd buy/borrow a book with pictures of how different handstitches are (if you are doing it by hand) =D
Her stockings can be easily bought since black is a common stocking color =D
Same with her shoes. They look like Mary Janes that are black.
For her skirt, you can buy a pattern for a simple pleated skirt. You might be able to find a white pleated skirt that length at a store though.
The shirt would probably be the hardest part. You can a.) buy a long-sleeved shirt and add a sailor collar and bow to it or b.) make it by hand. If you are going to make it by hand, then you can buy a pattern for a simple sweater and add a sailor collar and bow to it.
If you don't feel like buying a pattern but still want to make it by hand, you can make your own patterns with existing clothes by tracing them (this took me a bit to get used to, but it's worth it since patterns are kinda expensive).
I hope I helped ^_^ and good luck!