Keirii21: your picture is so large that the ads cover the character you are referencing :/
Quackalackin: If your grandma knows how to sew, she will be able to find the right fabric for that uniform type outfit. It's a good starting point, take full advantage of a teacher!
kitee: yes, cotton sateen would look quite nice. You can always line or innerface it if it's not substantial enough.
Sporkster: linen or something that looks like linen would be quite nice.
SparkyCat13: look to Kwik Sew patterns, they have a lot of 'athletic' type patterns that work great for lots of cosplays.