I guess it is also important who you would like to perceive you as young, sexy etc. If the answer is yourself, then no one can tell you what to wear, only you can decide. If it is other people, I am afraid there is no unique answer, not even as general as some notes or perfume groups. As you can see from the answers, everyone seems to have a different view of a sexy perfume. In fact, I am pretty sure we have different views on "sexy".
My guess is that some (younger?) people might associate "sexy perfume" with the perfume they smelled on many young, hot, sexy girls. Could be Pink Sugar or Bath and Body Works or whatever. Others might have specific and various ideas:leather is sexy, or vanilla is sexy, vintage chypre is...
Personally I find sweet, heavier, vanillic perfumes quite sexy. My husband (32) finds Shalimar, Addict, Blue Amber, pretty much all vanilla scents disgusting and "food like". Obviously not sexy!
My point is it's impossible to find a scent that will please everyone. And as someone said before, if you are all those things, any perfume you wear and enjoy will be perceived as pretty nice!