What is sexy? Is is your body? Is it your mind? Is it your vibration? Or is it a combination of all of these?
I am of the opinion that it is more than just looks. Although the VERY first thing is looks, after that there is more.
If two people have equivalent sexy looks, one of them can still be much sexier than the other.
So do the best you can to tone your body, and dress sexy of course. After that, have a sexy attitude and you will rise above other of equal visual appeal.