I'm a fashionista and these are the three types of tops you should avoid at all costs if you're flat chested
Women Super Flat Chest Binder Lesbian Tank Tops Tomboy Elastic Band Chest Vest (Black, US XS/Tag Asian M(Bust 29.9-31.5)) at Women's Clothing store
Cute bustier/corset style tops that fit small chests (similar style to this but better fitting)? : r/findfashion