Kill La Kill and Sailor Uniform (Cosplay help)

okay so i'm quite new to the anime (I watch it in dub because i prefer it that way and haven't got to see 20-25 yet) anyway I really like Satsuki and I want to cosplay her in future cons, most cosplays I see of her are well the main 2, I like her simple school uniform from when she was younger (shown in picture) but I cant find a uniform like that (like if it has a name) IK it would be easier to make it or have it made, so my question is, where or if i can find a uniform like hers, did someone cosplay this outfit (picture) ive asked this in yahoo a week ago so i came here because you guys are really helpful.
If you read all of that and helped me out that you so much!