Welcome to basenotes. I'm glad you joined up! Now you can asked all the questions you've been wondering and I'm more than glad to answer what I can. I don't try to know everything... or do I....
I think you have 3 really great choices for you age, social situation, and function. I would hope that you have looked up the reviews for these scents because the note pyramids can be missleading. Here are my views on these scents.
Body Kouros - YSL is truely unique but this is not one of the scents that exhibits that great side of this house. It is a sweet oriental. It is one of my favorite sweet orientals. It is sugary, and I think it will get you a little more attention. You have to be careful and spray this one in moderation as you don't want to be pissing anyone's nose off.
Rive Gauche - Woody and masculine. It has patchouli and vetiver, which work very well in this scent. I don't smell the patchouli but that is just my nose. I think that you will get more attention with this scent because it is far more unusual, but not in a negative way.
Gucci Envy - This is a combination of the first two. It is a woody oriental. It's masculine and sweet with spices and woods mellowing out to a nice warm base. It is one of my favorites and very popular for you age. I think it is the best choice for you, so far. It was one of the first fragrances I bought. It was love at first sniff. That never happens.
Those are my thoughts on what you have chosen. I would add something refreshing with citrus or aqua notes to balance out the group. Otherwise, you'll have nothing to wear in the summer. I acutally like Rive Gauche in the summer but you might want something else to go with it. My suggestions in order of how much I like them are: Geir(Geir Ness), Neroli Sauvage(Creed), Live Jazz(YSL)
Good luck on your hunt. I hope your picks end up being what you thought they would be.