What's the biggest size that you can start up with for breast implants?

Without examining you or even seeing photos of your anatomy there is no way to provide you with the commentary you want.  See a BC PS in person to discuss this.

Without more info (photos, measurements of the breasts) the question cannot be answered. There are patients in whom 400 cc is too large to insert, others who can get 800 cc (the largest gels) without a problem. Your surgeon who had all the info he needed probably gave appropriate advice to you.Best wishes.

Other than the size being absurd in appearance, there is not really a limitation in size of implants that can be inserted. I have inserted 900 cc saline implants and 800cc silicone implants during an initial augmentation.