I would recommend going somewhere and getting fitted properly. That doesn't necessarily have to mean somewhere expensive. I don't know where you live but I've been fitted well at a reasonably priced department store and waited for a good sale. I'm a 34 DD and I've done well with some Warners and some Wonderbra. I generally stay away from Victoria Secret. They're not cheap and I find the support of the bras to be so-so.
Comfort and preference is all a matter of opinion but I like something with an underwire and seamless so it doesn't show through a T-shirt. I say go somewhere, get fitted, try a whole bunch on and buy one or two. If you like it, then look online for the best prices. I could never buy a bra without trying it on.
Good Luck!