For shirts, look at Bravissimo/pepperberry and biubiu and urkye, they all make shirts for boobs
bra wise, you will ptobably need to try both. Most people get on best with the size below what they measure unless they are very slender. sizes to try would be 32d/dd and 34c/d. what are you wearing just now?
Minimisers are tricky, as all they do is shove your boobs under your armpits!