As far as teachers go, I sent an group e-mail to my teachers, and cc'd my class counselor and vice principal. That way, I had my bases covered, all the staff knew, and the admins would know ahead of time to look out for any discrimination from teachers toward me (which was never the case, but it was a good safeguard). They probably won't be able to change your name or gender, since they'll want your legal name and gender in their systems, but if you tell your teachers your preferred name and stick with correcting them, it won't be so bad (unless there's a substitute, but what can you do?). As teachers started calling me Andrew, even kids I didn't go "hi I'm trans" to seemed to pick up on it and just rolled with it accordingly. I don't know where you're located, but I doubt everyone would think you're ill.
Also, have you asked your mom about maybe footing the bill on a binder and letting you pay her back when you have the funds? You might be able to speed ship an Underworks one in time.