“No matter” what you wear, your outfit will make you appear fashion if it suits you so much that everybody can perceive your feeling at ease and fine.
With prèt à porter it may be easier as you have a lot of options and accessories. With sports clothes it may be challenging as you only can wear a few pieces on your skin and you have to practise sports.
For example, for women the top or bra is very important. It is something that makes the difference between a sexy, but professional clothing, and a technical clothing tout-court.
Being sexy in the gym is very delicate, almost diplomatic. If you wear too sexy, then maybe you are not working really hard. On the contrary, it is not sexy at all working hard without the right technical clothing. Why? Because hard work requires passion and knowledge and the more you train, the more you become exigeant. Professionals know it.
Therefore, do not be shy or do not use the gym to hook. Eyes and smile are “yes or no” to post-gym invitations. Be sexy, with technical clothing. When in doubt, go for technical, not for sexy, as what really matters is not the size of your breast, but the way you move on the technical equipment, the way you do the exercise. In the gym, hormones arises from body first, properly optimized by right clothing. Technical is always right. Not technical is your creative risk. I love taking risks, but I have to admit, that, as I seriously train, I need to move first.
How to chose a Bra? Less sew as possible as in Mat activities you have to lay down and press your breast and back. Try it in all position as in the gym you will move upside down with mirrors and eyes everywhere. Prepare yourself as the gym is not a place for shy people.