I know you don't want to spend the money, but I really suggest going somewhere like Nordstrom and getting a bra fitting.

A good bra fitter works magic just like a good bike fitter.

Buy one good all-rounder bra in exactly your size as it is *right now.* Don't shy away from underwire, if the bra fits right the underwires won't poke anything. You could be surprised.

My $70 bra wasn't cheap, but when I add up all the cheap bras I bought which didn't fit, or hurt, or slid off my shoulders, or drove me crazy... well, it would've been cheaper for me to just go buy the one $70 bra instead.