24yo 5'10 143lbs, A cup to full C small D

Starting at an A and hoping to fill a full C. I don't want to go too big, and I don't want to fit a small D. Doctor suggested 400-475cc but I don't know if that's too much? I was thinking 350-375, maybe 400. But I'm tall so I don't know. It makes me anxious I wish I could know how much I need for my perfect size. Of course everyone says they wish they'd gone bigger but I like small boobs. I just do like being flat chested a so tall, I feel unproportionate.
I haven't set a date yet. I do massage therapy so I will need 4-6 weeks off work and I can't afford that right now.

36A hoping for a full C

36A wanting to fill a full C