@Francesca, I encourage you to give it a try. The sewing part is straightforward, especially if you follow Beverly’s classes. Fitting can be a bit of a journey for some, and you may have to make a few test bras, but less precious fabrics can be used to get you most of the way there.
The most important place to start is finding your personal best fitting underwire.
They come in different lengths and shapes. Bras are designed around different length and styles of underwires, but you can usually substitute your best fitting underwire in terms of shape and length, not style. It should follow your underbust crease where it meets the chest wall as exactly as possible. Once you have the correct underwire, the bridge may be altered to fit if necessary. The cups are then fitted and lastly the band and straps.
Approaching it this way is recommended by many experts and is also outlined in the bra fitting book by Orange lingerie.
I think you may have more luck with high quality steel wires. These are sold by many bra suppliers and are available in heavy gauge.
I’m still a novice myself, but have gleaned much info from those who have made many bras.
One day I might even take a stab at drafting my own