Sports Bra for First Tri

It really depends on your size and what level of support you're comfortable with. I'm not that big (34 A or B depending on brand) and get by with the built-in bra in my tri-suit; many women find it's not enough, though. When I do need a bra for biking and running (or if I wear my tri-suit that doesn't have a built-in bra), I usually wear a kind of "sports bra" from Danskin that's sold at Walmart. Nothing fancy but I like it as there are no hooks or anything to rub or scratch, and it comes in different colors. It's fine for me even for a 3-hour ride or 2-hour run. The same brand also has sports bras with more support for larger women or those who just feel more comfortable with a bit more substantial bra. I think the key is to keep anything that might rub (fasteners, lacy trim) to an absolute minimum or avoid it, while getting the level of support you need.

BTW Danskin also makes some really nice women's tri tops with built-in bras and nice colors, which are cheaper than a lot of the well-known tri brands like Zoot, Sugoi, and 2XU. I get mine at REI in Oregon; possible that Dick's might stock them. They run a longer than those brands as well, which is nice if, like me, you're long-waisted and/or don't like tops that ride up and expose the tummy.

As Hotrunner said, the best bra for you will depend on your size. FWIW, I wore a padded bra for my first tri (as homage to my mother who can't stand to know when a woman is cold.) and I wish I had worn a non-padded one. That water stayed in that bra the whole time and added extra weight. And as for the style, I think simple razor back is best for swimming. I have some cuter sports bras with no slipping little straps but I wear them only for running because I'm afraid the straps might not be as comfortable for swimming. Good luck in your tri!