Help needed for bras

Honestly speaking, at this point I don't know what my measurements are anymore. I live in India, so the first size for bra here is 32 B. I am way below it. The training bras are just like wearing a tight petticoat. I am currently wearing a 30C bra brought by my Aunt from London, she said that was the only small size she could find in the shop.

My sizes are bust- 31 half inch, below bust- 26 inch. (I can go to 25 if I pull the tape hard)

I need to buy sports bras more than the regular ones.

The problem is If i buy the bras with small band, the cup are very small and if I buy a bra with fits my cups, the band will be super loose.

I haven't bought a bra online as of now. It's not even that I am too thin or something. I am just as an avg girl of my age (16) would be.

Also I would like it if I got these bras from sites which don't cost me a lot of shipping fees haha